Minimally invasive spinal fixation system and related methods

ABSTRACT

This application describes surgical instruments and implants for building a posterior fixation construct across one or more segments of the spinal column. Extension guides are provided that attach to bone anchors implanted within the spine. The extension guides have a guide channel that align with a rod channel in the anchor to help direct the rod to the anchor. Instruments are provided to aid in insertion and positioning or the rod.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/949,280, filed on Nov. 23, 2015, now U.S. Pat. No. 9,649,140, whichis a continuation of U.S. patent application Ser. No. 13/456,210, filedon Apr. 25, 2012, now U.S. Pat. No. 9,198,698, which is acontinuation-in-part of U.S. patent application Ser. No. 13/371,370,filed on Feb. 10, 2012, now U.S. Pat. No. 9,198,692, which claims thebenefit of priority from U.S. Provisional Patent Application Ser. No.61/441,283 filed on Feb. 10, 2011 and U.S. Provisional PatentApplication Ser. No. 61/444,698 filed on Feb. 18, 2011, the entirecontents of which are each hereby expressly incorporated by referenceinto this disclosure as if set forth in its entirety herein. Thisapplication also claims the benefit of priority under 35 U.S.C. 119(e)from U.S. Provisional Patent Application Ser. No. 61/478,658 filed onApr. 25, 2011 and U.S. Provisional Patent Application Ser. No.61/553,052 filed on Oct. 28, 2011, the entire contents of which are eachhereby expressly incorporated by reference into this disclosure as ifset forth in its entirety herein.

FIELD

This application describes surgical instruments and implants forbuilding a posterior fixation construct across one or more segments ofthe spinal column.

BACKGROUND

Spinal fixation constructs are utilized to provide stability to thespine. Most often the fixation construct is used as an adjunct to fusionsurgery during which adjacent vertebrae are prepared to facilitate bonegrowth between them, thereby eliminating motion between the vertebrae.Because motion between the vertebrae tends to inhibit bone growth, thefixation constructs are employed to prevent motion so that bone can growand achieve a solid fusion. When the position of one or more vertebraemust be adjusted to restore a more natural alignment of the spinalcolumn, the fixation construct also serves to maintain the new alignmentuntil fusion is achieved. Fixation constructs of various forms are wellknown in the art. Most commonly, the fixation construct is a plateanchored to the anterior column with multiple bone anchors or aposterior fixation construct including multiple anchors and a connectingrod anchored to the posterior elements of the spine. For a posteriorfixation construct the anchors (typically pedicle screws) are anchoredinto the pedicles of each vertebra of the target motion segment. Theanchors are then connected by a fixation rod that is locked to eachanchor, thus eliminating motion between the adjacent vertebrae of themotion segment. The posterior fixation construct may be appliedunilaterally or bilaterally. Additionally the posterior fixationconstruct may be applied across multiple levels or motion segments.

The fixation anchors utilized in posterior fixation constructs generallyinclude an anchor portion and a rod housing. The rod housing includes apair of upstanding arms separated by a rod channel in which the fixationrod is captured and locked. When constructing the posterior fixationconstruct the surgeon must align and seat the rod in the rod channel.This can be a challenge, particularly when one or more of the vertebraeto be connected is out of alignment leaving the associated anchor offsetvertically and/or horizontally from the remaining anchor(s) of theconstruct. Constructing the posterior fixation construct under minimallyinvasive access conditions (e g minimizing overall incision length andmuscle stripping as compared to traditional open procedures) alsoincreases the difficulty of aligning the rod with the rod channel of theanchor.

The instruments, tools, and techniques described herein are directedtowards reducing these challenges and others associated with posteriorspinal fixation.

BRIEF DESCRIPTION OF THE DRAWINGS

Many advantages of the present invention will be apparent to thoseskilled in the art with a reading of this specification in conjunctionwith the attached drawings, wherein like reference numerals are appliedto like elements and wherein:

FIG. 1 is a perspective view of the spinal fixation anchor according toan example embodiment;

FIG. 2 is a perspective view of an implantable portion of the fixationanchor of FIG. 1 after removal of an extension guide;

FIGS. 3-4 are side and front views, respectively, of the spinal fixationanchor of FIG. 1;

FIG. 5 is an enlarged perspective view of the junction between theimplantable portion and extension guide of the fixation anchor of FIG.1;

FIG. 6 is an enlarged front view of the junction region between theimplantable portion and extension guide of the fixation anchor of FIG.1;

FIG. 7 is a side view of a breaking tool, according to an exampleembodiment;

FIG. 8 is an exploded perspective view of the breaking tool of FIG. 7;

FIG. 9 is a front view of the fixation anchor of FIG. 1, after proximaljoints are broken to allow the arms to separate;

FIG. 10 is a perspective view of a guide cap for use with the fixationanchor of FIG. 1, according to one example embodiment;

FIG. 11 is another perspective view of the guide cap of FIG. 10;

FIG. 12 is a side view of the guide cap of FIG. 10;

FIG. 13 is a cross section view of the guide cap as shown in FIG. 12;

FIG. 14 is a perspective view of the guide cap of FIG. 10 coupled to thefixation anchor of FIG. 1;

FIG. 15 is a perspective view of an independent reduction tool that maybe used with the guide cap and fixation anchor of FIG. 14;

FIG. 16 is a front view of the independent reduction tool coupled to theguide cap and fixation anchor of FIG. 14;

FIG. 17 is a perspective view of a lumbar spine illustrating the use ofspinal fixation anchors of FIG. 1 with the guide cap of FIG. 10 andindependent reduction instrument of FIG. 15 to implant a two levelfixation construct, according to one example;

FIG. 18 is a perspective view of the lumbar spine of FIG. 17 after thelocking caps have been deployed and extension guides have been removedto leave the final fixation construct;

FIGS. 19-20 are perspective and side views, respectively, of a lumbarspine illustrating the use of a spinal fixation system according to oneexample embodiment;

FIG. 21 is a perspective view of an example of a guide assembly formingpart of the spinal fixation system of FIG. 19;

FIG. 22 is a perspective view of the distal end of the guide assembly ofFIG. 21;

FIGS. 23-24 are perspective views of an inner member forming part of theguide assembly of FIG. 21, shown without the outer sleeve;

FIGS. 25-26 are sectional views of the inner member of FIG. 23;

FIG. 27 is a plan view of the distal end of the guide assembly of FIG.21;

FIGS. 28-29 are perspective views of an example of a pedicle screwforming part of the spinal fixation system of FIG. 19;

FIGS. 30-31 are perspective and plan views, respectively, of one exampleof a tulip forming part of the pedicle screw of FIG. 28;

FIG. 32 is a perspective view of the guide assembly of FIG. 21 engagedwith a pedicle screw of FIG. 28;

FIG. 33 is a plan view of the distal end of the guide assembly of FIG.21 engaged with the tulip of FIG. 30;

FIG. 34 is a sectional view of the distal end of the guide assembly ofFIG. 21 engaged with the tulip of FIG. 30;

FIG. 35 is a plan view of a second example of a guide assembly foil lingpart of the spinal fixation system of FIG. 19, shown in an unlockedconfiguration;

FIG. 36 is a plan view of the guide assembly of FIG. 35, shown in alocked configuration;

FIG. 37 is a plan view of the distal end of the guide assembly of FIG.35;

FIGS. 38-39 are plan and perspective views, respectively, of a secondexample of a tulip forming part of the pedicle screw of FIG. 28;

FIGS. 40-41 are plan and sectional views, respectively, of the distalend of the guide assembly of FIG. 35 coupled with the tulip of FIG. 38;

FIGS. 42-44 are plan, perspective, and exploded perspective views,respectively, of a third example of a guide assembly forming part of thespinal fixation system of FIG. 19;

FIG. 45 is one example of a spinal rod forming part of the spinalfixation system of FIG. 19;

FIGS. 46-48 are perspective, side plan, and end plan views of one end ofthe spinal rod of FIG. 45;

FIG. 49 is another example of a spinal rod forming part of the spinalfixation system of FIG. 19;

FIGS. 50-52 are perspective, side plan, and end plan views of one end ofthe spinal rod of FIG. 49;

FIG. 53 is a plan view of an example of an adjustable angle rod inserterconfigured for use with the spinal fixation system of FIG. 19, shown ina first position;

FIG. 54 is a plan view of the rod inserter of FIG. 53, shown in a secondposition;

FIG. 55 is a plan view of the rod inserter of FIG. 53 coupled with aguide assembly of FIG. 21;

FIG. 56 is a sectional view of the rod inserter of FIG. 53;

FIGS. 57-58 are sectional views of the distal end of the rod inserter ofFIG. 53;

FIG. 59 is a plan view of one example of a fixed angle rod inserterconfigured for use with the spinal fixation system of FIG. 19;

FIG. 60 is a plan view of the rod inserter of FIG. 59 coupled with aguide assembly of FIG. 21;

FIG. 61 is a sectional view of the distal end of the rod inserter ofFIG. 59;

FIG. 62 is a plan view of another example of a fixed angle rod inserterconfigured for use with the spinal fixation system of FIG. 19;

FIG. 63 is a sectional view of the distal end of the rod inserter ofFIG. 62;

FIGS. 64-65 are perspective views of one example of a reductioninstrument configured for use with the spinal fixation system of FIG.19;

FIG. 66 is a top plan view of an example of a lock screw forming part ofthe spinal fixation system of FIG. 19;

FIG. 67 is a sectional view of the reduction instrument of FIG. 64;

FIG. 68 is a plan view of the reduction instrument of FIG. 64 coupledwith a guide assembly of FIG. 21, which in turn is coupled to a pediclescrew of FIG. 28;

FIG. 69 is a sectional view of the distal end of the reductioninstrument of FIG. 64 coupled with the lock screw of FIG. 66;

FIG. 70 is a sectional view of the reduction instrument and lock screwof FIG. 69 in combination with the guide assembly and pedicle screw ofFIG. 68 upon reduction of the spinal rod and before engagement of thelock screw to the tulip;

FIGS. 71-72 are sectional views of the distal end of another example ofa reduction instrument configured for use with the spinal fixationsystem of FIG. 19, shown coupled with a lock screw of FIG. 66;

FIGS. 73-74 are perspective and plan views, respectively, of thereduction instrument of FIG. 71 coupled with a lock screw of FIG. 66;

FIGS. 75-77 are plan views of another example of a reduction instrumentconfigured for use with the spinal fixation system of FIG. 19;

FIGS. 78-79 are plan and perspective views, respectively, of yet anotherexample of a reduction instrument configured for use with the spinalfixation system of FIG. 19;

FIG. 80 is a plan view of the distal end of the reduction instrument ofFIG. 78;

FIG. 81 is a sectional view of the reduction instrument of FIG. 78;

FIG. 82 is a plan view of still another example of a reductioninstrument configured for use with the spinal fixation system of FIG.19;

FIG. 82A is a sectional view of the reduction instrument of FIG. 82;

FIG. 83 is a plan view of the reduction instrument of FIG. 82 coupledwith a pedicle screw of FIG. 28;

FIGS. 84-85 are perspective and sectional views, respectively, of thedistal end of the reduction instrument and pedicle screw combination ofFIG. 83 shown during reduction of a spinal rod;

FIG. 86 is an example of a compression instrument configured for usewith the spinal fixation system of FIG. 19;

FIGS. 87-88 are perspective views of another example of a compressioninstrument configured for use with the spinal fixation system of FIG.19;

FIG. 89 is a top view of the compression instrument of FIG. 87;

FIG. 90 is a plan view of an example of a multi-load lock screw inserterconfigured for use with the spinal fixation system of FIG. 19;

FIGS. 91-93 are plan views of the lock screw inserter of FIG. 90 coupledto various numbers of lock screws;

FIG. 94 is plan view of the lock screw inserter of FIG. 90 in use withthe guide assembly of FIG. 21;

FIG. 95 is a perspective view of the lock screw inserter of FIG. 90 withthe outer shaft removed for illustration;

FIG. 96 is a perspective view of the lock screw inserter of FIG. 90 withthe outer shaft and the spring shaft removed for illustration;

FIG. 97 is a perspective view of an example of a guide adjusterconfigured for use with the guide assembly of FIG. 21;

FIG. 98 is a perspective view of the guide adjuster of FIG. 97 coupledwith the guide assembly of FIG. 21;

FIGS. 99-100 are perspective and sectional views, respectively, of anexample of a tap guide for use with the spinal fixation system of FIG.19;

FIG. 101 is a perspective view of an example of an offset dilatorconfigured for use with the spinal fixation system of FIG. 19;

FIGS. 102-103 are perspective views of another example of an offsetdilator configured for use with the spinal fixation system of FIG. 19;

FIG. 104 is a plan view of a secondary dilator configured for use withthe spinal fixation system of FIG. 19;

FIGS. 105-106 are perspective views of an example of a rod inserterconfigured for use with the spinal fixation system of FIG. 19; and

FIG. 107-108 are sectional views of the rod inserter of FIG. 105.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure. The spinal fixation system disclosed herein boasts avariety of inventive features and components that warrant patentprotection, both individually and in combination.

The present application describes a spinal fixation system that may beutilized to form a fixation construct across one or more spinal levelsof a patient. The spinal fixation system may be especially useful informing fixation constructs across multiple spinal levels and/or spineswith alignment deformities requiring correction. The spinal fixationsystem includes bone anchors (e.g. anchors 16, 112, 206), anchor guides(e.g. 18, 116, 188, 224), rods (50, 114), and various instruments (e.g.reduction instruments, rod inserters, compression instruments, etc. . .. ) that can be used in various combinations to form the fixationconstruct. The spinal fixation system may used for the installation ofthe fixation construct under minimally invasive conditions. That is, theoverall length of skin incisions required to install the fixationconstruct may be minimized compared to traditionally open pedicle screwprocedures. For example, the spinal fixation system includes a guidethat extends distally out of the patient when the anchor is engaged tothe spine. An elongated rod channel through the guide helps direct therod into the proper position without requiring the extended incisionsneeded to fully expose the spinal segments to be fixated.

Turning to FIGS. 1-2, there is depicted a spinal fixation anchor 10,according to an example embodiment. The spinal fixation anchor includesintegral reduction features that may be utilized to seat a fixation rodin the anchor while realigning the position of the associated vertebrarelative to other vertebra associated with the fixation construct.Additionally, separate reduction tools that cooperate with the spinalfixation anchor may be utilized to help seat the rod and realign theassociated spinal segment. The fixation anchor 10 includes a bone anchor12 (e.g. shank with thread feature 14) suitable for stable fixation tovertebral bone and a housing 16 for capturing and locking a fixation rod50. Attached to the housing 16 is a break-off extension guide 18. Theextension guide 18 helps align the rod 50 with the housing 16 and alsohelps reduce the rod into the housing when necessary. After the rod 50is locked within housing 16 the extension guide 18 can be removed fromthe housing so the incision can be closed over the fixation construct(FIG. 2 depicts the fixation anchor with the extension guide 18completely removed).

The housing 16 has a base 20 that mates with the bone anchor 12 and apair of upstanding arms 22 a and 22 b separated by a rod channel 24. Thearms 22 a and 22 b are equipped with a locking cap guide and advancementfeature 26, such as by way of example, a helically wound flange featuredisposed on the interior face of each arm 22 a and 22 b. The locking capguide and advancement feature mates with a complementary guide andadvancement feature on a locking cap 51. The locking cap 51 engages theupstanding arms via the complementary guide and advancement features topress and lock the fixation rod 50 into the housing 16.

The housing 16 and anchor 12 may be mated with a polyaxial engagementsuch that the housing 16 can pivot relative to the anchor 12 in anydirection. The engagement may also be such that the pivoting movementmay be inhibited in one or more directions. By way of example, thehousing 16 and anchor 12 may be mated with a uniplanar engagement suchthat the housing pivots relative to the anchor 12 in a single plane. Thehousing 16 and anchor 12 may also be fixed such that no movement ispossible between the housing 16 and anchor 12.

Break-off extension guide 18 extends from the top of housing 16 andincludes a pair of extension arms 30 a and 30 b. Extension arm 30 aattaches to housing arm 22 a via an integral but breakable distal joint32 a. Extension arm 30 b attaches to the housing arm 22 b via anintegral but breakable distal joint 32 b. The breakable distal joints 32a and 32 b are formed by surface grooves which reduce the materialthickness along the entire junction between the extension arms 30 a, 30b and housing arms 22 a, 22 b, respectively, such that directing anappropriate force to the extension arm will snap the associatedbreakable joint. The extension arms 30 a and 30 b are dimensioned with alength such that the extension guide 18 extends from the housing 16 to alocation outside of the patient when the fixation anchor 10 is in afully implanted position and securely anchored to the vertebra. At aproximal end 34 of the extension guide 18 the extension arms 30 a and 30b come together to form a pair of integral but breakable proximal joints36. Opposed vertical surface grooves above the guide slots 38 reducematerial thickness along each junction between the extension arms 30 aand 30 b to form the breakable proximal joints 36.

Opposed guide slots 38 formed between arms 30 a and 30 b align with therod channel 24 of the anchor housing 16 to define an enclosed guidechannel 40 which is dimensioned to allow passage of a fixation rod 50.Utilizing the guide channel 40 to align the rod 50 with the housing rodchannel 24 reduces the need for fiddlesome manipulation of the housingand/or rod down near the target site, as well as the associated need tofully visualize the housing 16 during rod insertion. Thus, the overallsize of the incision required to implant a fixation construct usingfixation anchors 10 is significantly reduced compared to openprocedures. Though not necessary, after the anchor 10 is implanted, andto help facilitate rod insertion, the proximal joints 36 may be broken,thereby severing the proximal connection of the extension arms 30 a and30 b and allowing the arms 30 a and 30 b to flex apart (FIG. 9). Afterbreaking the proximal joints 36, a guide cap 71 (described below) may beused to reassociate the extension arms 30 a and 30 b if desired. Recess40 a on the proximal end of extension arm 30 a and recess 40 b on theproximal end of extension arm 30 b facilitate the releasable coupling ofthe guide cap 71 to the proximal end 34 of the extension guide 18.

As best pictured in FIG. 5, the fixation anchor 10 includes an integralreduction feature which provides for effective, single step reductionand locking when the spinal alignment necessitates the rod be reducedinto the housing 16. The distal ends of extension arms 30 a and 30 b areappointed with a locking cap guide and advancement feature 42 situatedadjacent to the breakable distal joints 32 a and 32 b. The guide andadvancement feature 42 matches the guide and advancement feature 26 onthe interior face of arms 22 a and 22 b. Further, the guide andadvancement feature 42 is timed with the guide and advancement feature26 such that the locking cap 51 advances seamlessly from the extensionguide 18 to the housing 16. This configuration provides a mechanicaladvantage when advancing the locking cap 51 along the guide andadvancement features 42 and 26, allowing the locking cap 51 to drive therod into the housing 16 until it is fully seated and locked in position.

At some point during the surgical procedure after the fixation anchor(s)are anchored securely to their respective vertebra, the breakable distaljoints 32 a, 32 b and the breakable proximal joints 36 must be broken inorder to remove the break-off extension guide 18. The distal joints 32 aand 32 b are preferably broken only after the rod 50 is seated in thehousing 16 and the locking cap 51 is fully engaged. In the event theextension guide 18 is removed prematurely and a guide structure is stilldesireable (e.g. for rod insertion, locking cap engagement, and/orreduction purposes), an attachment groove 39 a is formed in the housingarm 22 a and an attachment groove 39 b is formed in housing arm 22 b. Aslip on guide structure (not shown) may be advanced and releasablycoupled to the housing via the attachment grooves 39 a, 39 b. Theproximal breaking joints 36 are preferably broken first beforeattempting break the distal joints 32 a, 32 b. This may be done justprior to breaking the distal joints to remove the extension guide afterthe rod 50 is seated and the locking cap 51 fully engaged in the housing16. Alternatively, the surgeon may want to sever the connection betweenthe extension arms 30 a, 30 b at an earlier point during the procedure.By way of example, the proximal joints 36 may be severed prior to rodinsertion in order to facilitate easier rod insertion.

With reference to FIGS. 7-8, an example embodiment of a breaking tool 44that may be utilized to break the proximal joints 36 is illustrated. Thebreaking tool 44 is designed to apply an outwardly directed force to theproximal joints 36 from inside the extension guide 18. The breaking tool44 is a cam driver and includes a handle 46, rotating drive shaft 48, acam 64 coupled to a distal end of the drive shaft 48, a hub 50, and acounter torque handle 52. The hub 50 has central cap 54 from which acylinder 56 extends distally and a faceted block 58 extends proximally.The cylinder 56 has an exterior diameter that is slightly smaller thanan interior diameter of the extension guide 18 such that the cylinder 56can be passed into the extension guide 18. The central cap 54 has adiameter that is larger than the extension guide 18 such that the cap 54controls the depth of insertion into the extension guide 18, ensuringforce is applied in the right locations (i.e. on or near the proximaljoints 36). The faceted block 58 mates with a complementary receptacle60 attached to the counter torque handle 52 to prevent rotation of thehub 50 when the drive shaft 48 is operated.

A tunnel 66 dimensioned to receive a portion of the drive shaft 48therethrough extends through the hub 50 along a line offset from acenter axis of the cylinder 56. The cam 64 has a diameter that matchesapproximately the diameter of the cylinder 56 and a tunnel 68 forreceiving the drive shaft 48 that is offset from the center axis of thecam. The cam 64 is fixed to the drive shaft 48 via pin 70 such thatrotation of the drive shaft 48 causes the cam 64 to rotate relative tothe cylinder 56. When the cam 64 and cylinder 56 are aligned they canslide together into the extension guide 18. As the cam 64 is rotatedrelative to the cylinder 56 the combined diameter of the two componentsexpands, directing an outward force onto the extension arms 30 a, 30 bwhich causes the breakable proximal joints 36 to break, allowing theextension arms 30 a, 30 b to separate, as shown in FIG. 9. With theproximal joints 36 severed, the distal breakable joints 32 a and 32 bcan be broken simply by bending the associated extension arm until thejoint snaps. This can be done using a common grasping tool, such asforceps for example, or grasping the extensions arms directly with thehand.

While breaking the proximal joints 36 may have desirable consequencesprior to and during rod insertion, it may also be desirable to have therigidity associated with the unbroken guide extension 18 at later pointsduring the surgery. To this end, a guide cap 71 is provided which may beused to hold the arm extensions 30 a and 30 b together and restore therigidity of the unbroken guide extension 18. The guide cap 71 has a body72 with a first internal cavity 73 opening out to a distal end 74 and asecond internal cavity 76 opening out to a proximal end 78. The firstinternal cavity 73 has an internal diameter that is just larger than theexternal diameter of the extension guide 18 such that the proximal endof the extension guide may be received in the first internal cavity 73.The second internal cavity 76 has a diameter smaller than the firstinternal cavity 73, to provide a shelf for spring 88, approximating theinternal diameter of the extension guide 18 and large enough to pass alocking cap 51 therethrough. A pair of opposed projections 80 extendinto the first internal cavity 73 and engage with the recesses 40 a and40 b on the extension arms 30 a and 30 b to releasably couple the guidecap 71 to the extension guide 18. The recesses 40 a and 40 b eachinclude an open vertical slot 82 connected to one end of a horizontalslot 84, and a closed vertical slot 86 connected to the opposite end ofthe horizontal slot. To attach the guide cap 71, the projections 80 arealigned with the open vertical slots 82 and pressure is applied to theguide cap 71 such that the cap advances onto the extension guide 18.When the projections 80 reach the bottom of the open vertical slot 82the cap is rotated until the projections 80 reach the end of thehorizontal slot 84. Pressure is then released from the guide cap 71 anda spring 88 working against proximal tabs 41 a, 41 b of the extensionarms draws the projections 80 into the closed vertical slots 86, therebysecuring the guide cap 71 to the extension guide 18.

The reduction capabilities of the extension guide 18 are enhanced withthe use of the guide cap 71. By way of example, the integral reductionfeatures described above are less effective when the extension arms 40 aand 40 b are flexible and allowed to splay. The guide cap 71 negatesthis challenge such that the surgeon is not required to choose betweeneasier rod insertion or better reduction. In addition, the body 72 ofthe guide cap 71 is adapted to releasably mate with independentreduction instruments should such an instrument be desired over theintegral reduction features of the extension guide 18. One example ofsuch an independent reduction instrument is depicted in FIG. 15.

The reduction instrument 92 includes a connector 96 that releasablycouples the reduction instrument to the extension guide (via guide cap71). The connector 96 has a receptacle 100 into which the proximal end78 of the guide cap 71 is received. The proximal end 78 is keyed to thereceptacle 100 so as to prevent rotation of the guide cap 71 andattached extension guide 18 relative to reduction instrument 92. Springclips 102 on the connector engage a groove 90 situated below theproximal end 78 to prevent translation of the guide cap 71 and attachedextension guide 18 relative to the reduction instrument 92. The springclips 102 have a tapered distal edge that extends into the receptacle100. The tapered edge allows the proximal end 78 to push past the springclips 102 until the tapered edge returns to rest in groove 90. Torelease the connection between the reduction instrument 92 and the guidecap 71 the proximal ends of the spring clips can be depressed and theconnector 96 lifted off the proximal end 78. In use, the reduction shaft94 is inserted through the guide cap 71 into extension guide 18 untilthe proximal end 78 of the guide cap 71 is locked into the receptacle100, as illustrated in FIGS. 16-17. A reduction handle 104 may then beoperated to translate the reduction shaft 94 distally relative to theextension guide 18 to drive the rod 50 through the guide channel 40until the rod is fully seated in the housing 16. A locking cap driver105 may then be operated to advance the locking cap 51 into the housing16 and lock the rod 50 in place.

Having described the various features of the fixation anchor 10 andassociated instruments, an example method for the minimally invasiveimplantation of a spinal fixation construct will now be described.First, a spinal fixation anchor is anchored through the pedicle of eachvertebra to be fixated (e.g. three vertebra as shown in FIG. 17). Atleast one of the spinal fixation anchors is the spinal fixation anchor10. The remaining fixation anchors may also be the fixation anchor 10(as in FIG. 17). Alternatively, the remaining fixation anchors may beanchors adapted for use with independent guide structures thatreleasably couple to the anchors, as are generally known in the art.

With the fixation anchors 10 in position, a rod 50 appropriately sizedto span the distance between the end anchors is selected. At this point,the proximal joints 36 on one or more of the fixation anchors 10 may bebroken if the surgeon chooses to do so. By way of example, the surgeonmay choose to break the proximal joints 36 of the fixation anchor 10 atthe opposite end of the construct from which rod insertion will bedirected. During some insertion techniques the rod is inserted into theguide channel of the first fixation anchor 10 generally parallel to theextension guide while the insertion instrument is angled back towardsthe remainder of the extension guides 18. As the inserter is rockedtowards the insertion end, the rod advances through each guide. Severingthe proximal joints 36 on the extension guide 18 at the opposite end ofthe construct from rod insertion allows the inserter to advance betweenthe extension arms 30 a, 30 b of the end anchor (instead of having towork the inserter around the outside of the guide extension 18). Thissimplifies passage of the rod by facilitating proper alignment of therod during insertion. If the surgeon chooses to break the proximaljoints 36, the cam 64 and cylinder 56 of the breaking tool 44 arealigned and inserted into the extension guide 18 until the cap 54 restson the proximal end of the extension guide 18. The cam 64 is thenrotated with one hand while the counter torque handle 52 is held in theother hand until the proximal joints 36 break apart. The rod 50 is theninserted through the guide channels 40.

If necessary, (for example, if the rod 50 does not fully seat within theanchor housing 16 as would be the case if or more of the vertebrae arenot vertically aligned) one or more of the reduction methods describedabove may be employed to reduce the rod 50. If the rod 50 is seated lowenough in the guide channel 40 that the guide and advancement features42 are accessible above the rod then reduction may be accomplished byengaging a locking cap 51 with the guide and advancement features 42 andadvancing the locking cap 51 until the rod 50 and locking cap 51 arefully seated in the housing 16. If this reduction is to be carried outon a fixation anchor 10 whose proximal joints 36 had been previouslybroken, the guide cap 71 should preferably be coupled to the extensionguide 18 prior to reduction. Alternatively, if the rod 50 sits above theguide and advancement features 42 or the surgeon simply prefers toutilize an independent reduction tool, the guide cap 71 should beattached to the appropriate fixation anchor 10 whether or not theproximal joints 36 of that anchor have been broken. The independentreduction instrument 92 is then coupled to the extension guide 18 andoperated to reduce the rod 50 into the housing 16 and a locking cap 51is engaged to lock the rod 50 in place. The surgeon may choose toutilize both the integral reduction features for reduction at onefixation anchor 10 and the independent reduction instrument forreduction at another of the fixation anchors 10. Reduction (whennecessary) and locking cap engagement is completed for each spinalfixation anchor in the construct.

With the rod 50 locked down along the entire construct the extensionguide 18 should be removed. First, any guide caps 71 utilized during theprocedure should be removed. Then the breaking tool 44 is used to breakthe proximal joints 36 of all extension guides 18 whose proximal joints36 remain intact. Finally, the extension arms 30 a and 30 b of eachspinal anchor 10 are removed by breaking the distal joints 40 a and 40b, respectively. According to an alternative sequence, the extensionguide 18 can be removed from each fixation anchor 10 in sequence as therod 50 is locked to each anchor 10. Once the extension guides 18 areremoved from each anchor 12, the final fixation construct is complete,as illustrated in FIG. 18, and the incision(s) can be closed.

FIGS. 19 and 20 illustrate a spinal fixation system 110 configured forintroducing and building a posterior spinal fixation construct such asthat described above, according to one example embodiment. According toone example, the spinal fixation system 110 includes a pedicle screw112, an elongated spinal rod 114, and a guide assembly 116. Pediclescrews 112 are inserted bilaterally or unilaterally into multiplevertebra across one or more levels. In addition, fixation anchor 10 canbe utilized in place of pedicle screw 112 in one or more vertebra. Thespinal fixation system 110 may further include any of a variety ofinstruments configured to perform the installation and assembly of thespinal fixation construct, including by way of example a reductioninstrument 117 shown in FIGS. 19 and 20, as well as rod inserters,compression instruments, lock screw inserters, guide adjusters, tapguides, and dilators, of which various embodiments are described infurther detail below.

FIGS. 21-27 illustrate one example of a guide assembly 116 for minimallyinvasive implantation of the pedicle screw 112 and for guiding thespinal rod 114 into position. By way of example only, the guide assembly116 includes an outer sleeve 118 and a pair of inner arm members 120positioned within the outer sleeve 118. The arm members 120 areconfigured to releasably engage the housing 172 of the pedicle screw112. The arm members 120 are moveable between a first position and asecond position. When in the first “unlocked” position, the arm members120 are not engaged with in the pedicle screw 112. In the second,“locked” position, the arm members 120 are engaged with the pediclescrew 112, and the pedicle screw 112 is “locked” to the guide assembly116.

The outer sleeve 118 is a generally tubular member having a proximal end122, a distal end 124, and a lumen 126 extending longitudinally throughthe outer sleeve 118. The proximal end 124 includes a cap 128 that isconfigured to engage the inner arm members 120 (on the inside of the cap128) and a reduction instrument 117 (on the outside of the cap 128). Acircumferential groove 130 is positioned near the proximal end 122 andconfigured to receive the ridges 346 of the spring lock 344 of thereduction instrument 117. In this fashion, the guide assembly 116 may bereleasably coupled to the reduction instrument 117. The outer sleeve 118further includes a cylindrical recess 132 formed distally of thecircumferential groove 130 but in the proximal half of the outer sleeve118. The cylindrical recess 132 is configured to receive an actuator 134and is further configured to allow translation of the actuator 134 in aproximal/distal direction within the cylindrical recess 132. The outersleeve 118 further includes a pair of longitudinal slots 136 extendingproximally from the distal end 124 of the outer sleeve 118. Thelongitudinal slots 136 act in concert for form a channel 149 to guidethe spinal rod 114 to the surgical target site during implantation ofthe surgical fixation construct. By way of example only, the slots 136extend a little over half way along the outer sleeve 118. The slots 136effectively divide the distal portion of the outer sleeve 118 into firstand second outer anus 138. The distal end of the outer arms 138 eachincludes a distal extension 140. The distal extension 140 is anextension of the outer sleeve 118 however it is narrower in width thanthe outer sleeve 118. A ridge 142 dimensioned to engage the housing 172of the pedicle screw 112 is positioned on the interior surface of thedistal extension 140. The ridge 142 is configured to engage theattachment groove 182 of the housing 172 to releasably lock the guideassembly 116 to the pedicle screw 112. The ridge 142 includes a taperedsurface 144 that enables the ridge 142 to slide over the top of thehousing 172 of the pedicle screw 112 during the engagement process. Theouter sleeve 118 is further provided with a plurality of elongatedapertures 146 positioned opposite one another on either side of theouter sleeve 118 and configured to receive protrusions 154 of the innerarm members 120 to facilitate the secure engagement of the inner arms120 to the outer sleeve 118.

The arm members 120 are each comprised of an elongatedpartially-cylindrical member having a proximal end 148 and a distal end150. The proximal ends 148 of the arm members 120 are dimensioned to bereceived within the cap 128 of the outer sleeve 118. The arm members 120each include a proximal protrusion 152 extending laterally from theouter surface of the arm member 120 and dimensioned to extend through acorresponding slot 146 positioned within the cylindrical recess 132 ofthe outer sleeve 118 and fixedly engage the actuator 134. In thisfashion, translation of the actuator 134 causes translation the firstand second arm members 120. Additional protrusions 156 are positionedalong the arm members 120 such that they are aligned with and receivedwithin corresponding slots 146 in the outer sleeve 118. The distal ends150 of the members 120 are configured to securely receive the top of thehousing 172 of the pedicle screw 112. To facilitate this secureengagement, the distal ends 150 of the arm members 120 include aplurality of prongs 158 configured to extend vertically along the sidesof the housing 172 upon engagement, as will be explained in furtherdetail below. Additionally, a raised protrusion 160 is provided betweenthe prongs 158 to engage a recess 184 in the top of the pedicle screw112. The prongs 158 and raised protrusion 160 act in concert to preventrotation of the housing 172 of the pedicle screw 112 during implantationof the spinal fixation construct.

The actuator 134 is positioned on the outside of the outer sleeve 118and is fixedly attached to the inner arms 120. As stated previously,translation of the actuator 134 causes translation the inner arms 120. Aspring 162 is provided that exerts a force distally the actuator and theinner arms 120 in order to bias the actuator 134 and inner arms 120 in a“locked” position. A stopper 164 is provided within the cap 132 toprovide a distal stop for the spring 162 and the inner arms 120. Theinner arms 120 may optionally be provided with a plurality of smallerapertures 166 to aid in the sterilization process.

The pedicle screw 112 includes a bone anchor 168 (e g shank with threadfeature 170) suitable for stable fixation to vertebral bone and ahousing 172 for capturing and locking a spinal rod 114. The housing 172has a base 174 that mates with the bone anchor 168 and a pair ofupstanding arms 176 separated by a rod channel 178. The arms 176 areequipped with a locking cap guide and advancement feature 180, such asby way of example, a helically wound flange feature disposed on theinterior face of each arm 176. The locking cap guide and advancementfeature 180 mates with a complementary guide and advancement feature ona lock screw (not shown, but similar to the lock screw 119 shown anddescribed in relation to FIGS. 69-74). The lock screw 119 engages theupstanding arms 176 via the complementary guide and advancement features180, 376 to press and lock the fixation rod 114 into the housing 172.

The housing 172 and anchor 168 may be mated with a polyaxial engagementsuch that the housing 172 can pivot relative to the anchor 168 in anydirection. The engagement may also be such that the pivoting movementmay be inhibited in one or more directions. By way of example, thehousing 172 and anchor 168 may be mated with a uniplanar engagement suchthat the housing pivots relative to the anchor 168 in a single plane.The housing 172 and anchor 168 may also be fixed such that no movementis possible between the housing 172 and anchor 168.

The housing 172 further includes a pair of attachment grooves 182, oneattachment groove 182 formed in each of the upstanding arms 176. Theattachment grooves are dimensioned to receive the ridges 142 on theouter sleeve 118 of the guide assembly 116 to releasably lock the guideassembly 116 to the pedicle screw 112. The top of each arm 176 furtherincludes a recess 184 formed therein. The recesses 184 have acorresponding shape and are dimensioned to receive the raisedprotrusions 160 on the distal end of the inner arm members 120 of theguide assembly 116. This interaction helps to prevent rotation of thehousing 172 of the pedicle screw 112 during implantation of the spinalfixation construct.

FIGS. 32-34 illustrate the guide assembly 116 engaged to a pedicle screw112. In order to accomplish this, once the pedicle screw 112 has beenseated in the appropriate position in the surgical target site, theguide assembly 116 is advanced distally along the operative corridoruntil the distal end of the outer sleeve 118 contacts the housing 172 ofthe pedicle screw 112. The guide assembly 116 is then further advancedsuch that the ridges 142 snap into the attachment grooves 182 on thehousing 172. At this point the outer sleeve 118 is secured to thepedicle screw 112. The actuator 134 is then advanced in a distaldirection, which causes the simultaneous distal advancement of the innerarms 120 of the guide assembly 116. The inner arms 120 are advanced suchthat and until each pair of prongs 158 are positioned on either side ofthe upstanding arms 176 of the housing 172 and the raised protrusions160 are seated within recesses 184 on the housing 172. At this point theinner anus 120 are secured to the pedicle screw 112 and the housing 172is prevented from rotation relative to the guide assembly 116. Uponcoupling of the guide assembly 116 and the pedicle screw 112, theopposed guide slots 168 formed between the outer arms 138 of the outersleeve 118 of the guide assembly 116 align with the rod channel 178 ofthe housing 172 to define an enclosed guide channel 186 that isdimensioned to allow passage of a fixation rod 114. Utilizing the guidechannel 186 to align the rod 114 with the housing rod channel 178reduces the need for fiddlesome manipulation of the housing 172 and/orrod 114 near the surgical target site, as well as the associated need tofully visualize the pedicle screw 112 and/or the housing 172 during rodinsertion. Thus, the overall size of the incision required to implant afixation construct using the described fixation system 110 issignificantly reduced compared to open procedures. Once the rod 114 hasbeen seated in the housing 172 and secured with a lock screw 119 (asdescribed below), the guide assembly 116 may be removed from theoperative corridor. To accomplish this, a proximal force is applied tothe actuator 134, which will disengage the inner arms 120 from thehousing 172. The outer sleeve 118 may be disengaged from the housing 172by applying an appropriate amount of proximal force on the guideassembly 116. Once both the outer sleeve 118 and the inner arms 120 havebeen disengaged from the housing 172, the guide assembly 116 may beremoved from the operative corridor.

FIGS. 35-37 illustrate an example of a guide assembly 188 according toan alternative embodiment of the present invention for use with thespinal fixation system 110 described above. The guide assembly 188 issubstantially similar to the guide assembly 116 described above, suchthat repeat description of like parts is unnecessary. By way of exampleonly, the guide assembly 188 includes an outer sleeve 190 and a pair ofinner arm members 192 positioned within the outer sleeve 190. The armmembers 192 are configured to releasably engage the housing 208 of thepedicle screw 206 (FIGS. 38-39). The arm members 192 are moveablebetween a first position and a second position. When in the first“unlocked” position, the arm members 192 are not engaged with in thepedicle screw 206. In the second, “locked” position, the arm members 192are engaged with the pedicle screw 206, and the pedicle screw 206 is“locked” to the guide assembly 116. As with the guide assembly 116, theguide assembly 188 includes an actuator 194 that facilitates themovement of the arm members 192 from the first to the second position.

The guide assembly 188 is substantially identical to the guide assembly116 with the exception of two features that will be discussed in detailbelow. It is to be understood that any or all of other featuresdescribed in conjunction with the guide assembly 116 may be present withrespect to the guide assembly 188 in both structure and function.Therefore, repeat description of common features is not necessary. Inaddition to many of the features described in conjunction with the guideassembly 116, the guide assembly 188 includes a castle nut 196protruding from the top of the outer sleeve 190. The castle nut 196interacts with the actuator 194 and serves as a visual indicator ofwhether the guide assembly 188 is locked to the pedicle screw 206. Morespecifically, when the inner arm members 192 are in the first,“unlocked” position, the castle nut 196 protrudes from the top of theouter sleeve 190 (FIG. 35). When the inner arm members 192 are in thesecond position, the castle nut can be advanced (blocking return of theinner arm members), making the second position the “locked” position asthe guides cannot be disengaged from the pedicle screw 206. The guide is“locked” when the castle nut 196 sits flush the top of the outer sleeve190 (FIG. 36) and thus serves as a visual indication as to whether theguide assembly 188 is locked to the pedicle screw 206.

Referring to FIG. 37, the second major difference between the guideassembly 188 and the guide assembly 116 is in the distal engagement ends198 of the inner arm members 192. The distal ends 198 of the arm members192 are configured to securely receive the top of the housing 208 of thepedicle screw 206. To facilitate this secure engagement, the distal ends198 of the arm members 192 include a plurality of prongs 200 configuredto extend vertically along the sides of the housing 208 upon engagement.The prongs 200 differ from the prongs 158 in that each prong 200includes an additional cutout area 202 on a pedicle screw engagementsurface that interacts with the pedicle screw 206 to provide a moresecure engagement, as will be described below. As with the first exampledescribed above, a raised protrusion 204 is provided between the prongs200 to engage a recess 220 in the top of the pedicle screw 206. Theprongs 200 and raised protrusion 204 act in concert to prevent rotationof the housing 208 of the pedicle screw 206 during implantation of thespinal fixation construct.

FIGS. 38-39 illustrate a pedicle screw 206 configured for use with theguide assembly 188 according to an alternative example. The pediclescrew 206 is similar to the pedicle screw 112 described above in that itincludes a bone anchor (e.g. shank with thread feature—not shown)suitable for stable fixation to vertebral bone and a housing 208 forcapturing and locking a spinal rod 114. The bone anchor portion of thepedicle screw 206 is identical to the bone anchor portion of pediclescrew 112 described above. The housing 208 has a base 210 that mateswith the bone anchor and a pair of upstanding arms 212 separated by arod channel 214. The arms 212 are equipped with a locking cap guide andadvancement feature 216, such as by way of example, a helically woundflange feature disposed on the interior face of each arm 212. Thelocking cap guide and advancement feature 216 mates with a complementaryguide and advancement feature on a lock screw (not shown, but similar tothe lock screw 119 shown and described in relation to FIGS. 69-74). Thelock screw engages the upstanding arms 212 via the complementary guideand advancement features 216, 376 to press and lock the fixation rod 114into the housing 208.

The housing 208 further includes a pair of attachment grooves 218, oneattachment groove 218 formed in each of the upstanding arms 212. Theattachment grooves 218 are dimensioned to receive the ridges 195 (FIG.35) on the outer sleeve 190 of the guide assembly 188 to releasably lockthe guide assembly 188 to the pedicle screw 206. The top of each arm 212further includes a recess 220 formed therein. The recesses 220 have acorresponding shape and are dimensioned to receive the raisedprotrusions 204 on the distal end of the inner arm members 192 of theguide assembly 188. This interaction helps to prevent rotation of thehousing 208 of the pedicle screw 206 during implantation of the spinalfixation construct. The housing 208 also includes a plurality ofvertical cutouts 222 formed in each upstanding arm 212 on either side ofthe rod channel 214. The vertical cutouts 222 interact with the prongs200 of the inner arm members 192 to provide a more secure engagementbetween the guide assembly 188 and the pedicle screw 206. Morespecifically, the cutout areas 202 of the prongs 200 are complimentaryin shape to the vertical cutouts 222 on the arms 212 such that uponengagement, each prong 200 will contact at least three distinct surfacesof the corresponding upstanding arm 212. FIGS. 40-41 illustrate theguide assembly 188 engaged to the housing 208 of a pedicle screw 206.

FIGS. 42-44 illustrate an example of a guide assembly 224 according to athird example embodiment of the present invention for use with thespinal fixation system 110 described above. The guide assembly 224 issubstantially similar to the guide assemblies 116, 188 described above,such that repeat description of like parts is unnecessary. It is to beunderstood that any or all of other features described in conjunctionwith the guide assemblies 116, 188 may be present with respect to theguide assembly 224 in both structure and function. By way of exampleonly, the guide assembly 224 includes an outer sleeve 226 and a pair ofindependent inner arm members 228 positioned within the outer sleeve224. The arm members 228 are configured to releasably engage the housing228 of the pedicle screw 206 (FIGS. 38-39). The distal engagement regionof the arm members 228 and the interaction with the pedicle screw 206 isidentical to that described in relation to the guide assembly 188. Aswith the previously described examples, the arm members 228 are moveablebetween a first position and a second position. When in the first“unlocked” position, the arm members 228 are not engaged with in thepedicle screw 206. In the second, “locked” position, the arm members 228are engaged with the pedicle screw 206, and the pedicle screw 206 is“locked” to the guide assembly 224. Unlike the guide assemblies 116,188, however, the guide assembly 224 does not include the same actuatorto facilitate the movement of the arm members 228 from the first to thesecond position. As will be described below, the guide assembly 224instead has a castle nut 230 that acts as the actuator. The castle nut230 attaches directly to the arm members 228, and controls theadvancement (and retreat) of the arms.

In addition to many of the features described in conjunction with theguide assemblies 116, 188, the guide assembly 224 includes a castle nut230 protruding from the top of the outer sleeve 226. As with the guideassembly 188, the castle nut 230 serves as a visual indicator of whetherthe guide assembly 224 is locked to the pedicle screw 206. Morespecifically, when the inner arm members 228 are in the first,“unlocked” position, the castle nut 230 protrudes from the top of theouter sleeve 226. When the inner arm members 228 are in the second,“locked” position and engaged to a pedicle screw 206, the castle nut 230is flush with the guide and consequently not visible above the top ofthe outer sleeve 226 (FIG. 42).

Unlike the guide assembly 188 described, the castle nut 230 not onlylocks the position of the inner arms after the arms move into position,the castle nut 230 also acts as the actuator to control the translationof the inner arms 228. To do this the inner arms 228 are attacheddirectly to the castle nut 230. The proximal ends 232 of the inner arms228 include a groove 234 that is dimensioned to engage a correspondingridge 236 in the interior of the castle nut 230. Alternatively, theproximal ends 232 of the inner arms 228 may be provided with ridges thatare received within corresponding grooves formed in the interior of thecastle nut (not shown). Any combination of grooves and ridges may beemployed to mate the inner arms 228 with the castle nut 230. In anycase, by way of example only, the inner arms 228 may be mated with thecastle nut 230 via a ridge/groove interaction. A tool (not shown) may beattached to the castle nut 230 (for example via slot 238) to help rotatethe nut and lock or unlock the inner arms 228 and pedicle screw 206. Thegroove/ridge interaction between the castle nut 230 and the inner arms228 ensure that the castle nut 230 is able to rotate freely relative tothe inner arms 228 while still controlling translation. The guideassembly 224 may be provided with guide slots 240 that extendsubstantially the length of the outer sleeve 226. Relative to guideassemblies 116, 188, the longer guide slots 240 on the guide assembly224 are possible due to the absence of an actuator to controltranslation of the inner arms 228.

FIGS. 45-52 illustrate several examples of spinal rods 114, 114 aconfigured for use with the surgical fixation system described herein.By way of example, the spinal rod 114, 114 a may be provided in anylength corresponding to the number of spinal levels to be fixed. Thespinal rods 114, 114 a are generally cylindrical elongated rods. Thespinal rods 114, 114 a may be straight or curved. By way of exampleonly, the spinal rods 114, 114 a have a first end 242, 242 a that isgenerally rounded and a second end 244, 244 a that is configured toengage a rod inserter such as the rod inserter 250 shown and describedbelow in relation to FIG. 53. The second end 244, 244 a includes a post246, 246 a having a shape corresponding to the shape of the rod cavity266 on the rod inserter 250. By way of example only, the spinal rod 114includes a post 246 having a generally octagonal cross-sectionalfootprint. Post 246 a is similar but is wider and has a rounded edge.The post 246, 246 a also includes a recess 248, 248 a formed on an uppersurface of the post 246, 246 a and configured to receive the distal lip278 of the locking element 268 on the rod inserter 250. The recess 248,248 a and distal lip 278 cooperate to temporarily secure the rod 114,114 a to the rod inserter 250.

FIGS. 53-58 illustrate a first example of a rod inserter 250 configuredfor use with the spinal fixation system 110 according to one embodimentof the present invention. By way of example only, the rod inserter 250is an adjustable-angle rod inserter that introduces the spinal rod 114through the operative corridor at one angle (relative to the inserter),and then pivots the rod at the surgical target site. This enables longerspinal rods 114 to be inserted through an operative corridor, and italso allows for smaller incisions because less room is needed to insertthe spinal rod.

By way of example only, the rod inserter 250 includes an outer sleeve252, an inner shaft 254, a handle 256, and a rod holder 258. The outersleeve 252 is an elongated cylindrical member having an inner lumenextending throughout. The inner shaft 254 is an elongated rod memberhaving a knob 260 at the proximal end and an engagement post 262 at thedistal end. The knob 260 is configured for handling by a user, andallows to user to pull up (proximally) on the knob to disengage the post262 from the first and/or second shaft recesses 270, 274. The knob 260can also be rotated in a clockwise or counterclockwise direction inorder to lock or unlock the setscrew 272, as will be described below.The engagement post 262 is configured to engage the first and secondshaft recesses 270, 274 to maintain the rod inserter 250 in either thefirst or second position. A spring 264 is located within the handle 256and acts to bias the inner shaft 254 in a distal direction. This ensuresthat the rod inserter 250 is secured in either the first or secondpositions, and a positive action is required by the user to effect achange in position.

The rod holder 258 is pivotably attached to the distal end of the outersleeve 252, and is configured to be pivoted from a first position to asecond position and then back to the first position. The rod holder 258includes a rod cavity 266, a locking element 268, first shaft recess270, a setscrew 272, and second shaft recess 274. The rod cavity 266 isconfigured to receive the post 246 of the spinal rod 114. The lockingelement 268 is positioned within the rod holder 258 and is moveable froma first unlocked position to a second locked position. The lockingelement 268 includes a proximal recess 276, a distal lip 278, and acentral cavity 280. The proximal recess 276 is configured to receive thesetscrew 272, and is firmly attached to the setscrew via a snap ring282. The snap ring allows the setscrew 272 to rotate within the proximalrecess 276 while being advanced or retreated by the inner shaft 254, andalso ensures that the locking element 268 is advanced and/or retreatedalong with the setscrew 272. A lockstop 284 in the form of a pin (by wayof example only) extending through the cavity prevents the lockingelement 268 (and setscrew 272) from being retreated so much that itbecomes disengaged entirely from the rod holder 258. The distal lip 278is configured to be seated within the recess 248 of the spinal rod 114such that when the rod inserter is in the locked position, the spinalrod 114 is secured within the rod cavity 266 and will not becomedislodged therefrom. The setscrew 272 is positioned within the firstshaft recess 270. The second shaft recess 274 is configured to receiveengagement post 262 when the rod holder 250 is in the second position.This interaction temporarily locks the rod holder 250 in the secondposition.

In use, the rod inserter 250 is initially provided in a first position(FIG. 53) without the spinal rod 114 and the rod holder 258 in anunlocked position. In this first position, the first shaft recess 270(and consequently the setscrew 272) is in alignment with the centrallumen of the outer shaft 252. The spinal rod 114 is then mated with therod holder 258 by inserting the post 246 into the rod cavity 266 suchthat the recess 248 is facing the locking element 268. The knob 260 isrotated in a clockwise direction, which advances the setscrew 272 andlocking element 268 in a distal direction until the distal lip 278 ofthe locking element 268 is seated within the recess 248. At this pointthe spinal rod 114 is secured to the rod inserter 250. The user thenexerts a proximal force on the knob 260 causing the inner shaft 254 tomove in a proximal direction and further causing the engagement post 262to become disengaged from the first shaft recess 270. The rod holder 258will then pivot (due to the pull of gravity on the spinal rod 114) suchthat the second shaft recess 274 becomes aligned with the outer shaft252. The user may then release the knob 260, which due to the spring 264advances the inner shaft 254 distally and causes the engagement post 262to be received within the second shaft recess 274. The rod holder 258 isnow secured in the second position (FIG. 54). In the second position,the spinal rod 114 is positioned at an obtuse angle relative to the rodinserter 250, which reduces the size of the operative corridor requiredto advance the rod. The rod 114 may be advanced through the operativecorridor using a guide assembly such as the guide assembly 116 (or anyof the other examples) described above.

As the distal tip of the rod reaches the target site it may becomenecessary to pivot the rod to further its advancement. This may beaccomplished by once again applying a proximal force on the knob 260 torelease the engagement post 262 from the second shaft recess 274. Thisallows the rod holder 258 to pivot toward the first position. Once therod 114 is fully inserted, the user may release the knob 260 to reengagethe engagement post 262 and the first shaft recess 270. The rod holder258 is once again in the first position (FIG. 55). Once the rod 114 isseated within the pedicle screw 112 and secured as described above (andbelow), the rod 114 is ready to be detached from the rod inserter 250.To accomplish this, it is necessary to return the rod holder 258 to thefirst position (as just described) if it has not already been doneduring insertion of the rod. With the rod holder 258 in the firstposition, the knob 260 is turned counterclockwise to translate thesetscrew 272 (and locking element 268) in a distal direction, whichremoves the distal lip 278 from the recess 248 and unlocks the rod 114.The rod inserter 250 may then be safely removed from the surgical targetsite through the operative corridor.

FIGS. 59-61 illustrate a second example of a rod inserter 290 configuredfor use with the spinal fixation system 110 according to anotherembodiment of the present invention. By way of example only, the rodinserter 290 is a fixed-angle rod inserter that introduces the spinalrod 114 through the operative corridor at one angle (relative to theinserter).

By way of example only, the rod inserter 290 includes a housing tube292, a center screw 294, a handle 296, and a rod holder 298. The housingtube 292 is an elongated cylindrical member having an inner lumenextending throughout. The center screw 294 is an elongated rod memberhaving a driver engagement recess 300 at the proximal end and anengagement post 302 at the distal end. The driver engagement recess 300is configured to receive an engagement end of a suitable driverinstrument (not shown). The center screw 294 can be rotated in aclockwise or counterclockwise direction in order to lock or unlock thespinal rod 114 to the rod inserter 290, as will be described below. Theengagement post 302 is configured to engage the locking element 306. Aspring (not shown) is located within the housing tube 292 and acts tobias the locking element 306 in an unlocked position.

The rod holder 298 is formed in the distal end of the housing tube 292.The rod holder 298 includes a rod cavity 304 and a locking element 306.The rod cavity 304 is configured to receive the post 246 of the spinalrod 114. The locking element 306 is positioned within the rod holder 298and is moveable from a first unlocked position to a second lockedposition. The locking element 298 includes a proximal recess 308 and adistal lip 310. The proximal recess 308 is configured to receive theengagement post 302. The distal lip 310 is configured to be seatedwithin the recess 248 of the spinal rod 114 such that when the rodinserter 290 is in the locked position, the spinal rod 114 is securedwithin the rod cavity 266 and will not become dislodged therefrom.

In use, the rod inserter 290 is initially provided without the spinalrod 114 and the rod holder 298 in an unlocked position. The spinal rod114 is then mated with the rod holder 298 by inserting the post 246 intothe rod cavity 304 such that the recess 248 is facing the lockingelement 306. The center screw 294 is rotated in a clockwise direction,which advances the locking element 306 in a distal direction until thedistal lip 310 of the locking element 306 is seated within the recess248. At this point the spinal rod 114 is secured to the rod inserter290. The rod 114 may be advanced through the operative corridor using aguide assembly such as the guide assembly 116 (or any of the otherexamples) described above. Once the rod 114 is seated within the pediclescrew 112 and secured as described above (and below), the rod 114 isready to be detached from the rod inserter 290. To accomplish this, thecenter screw 294 is turned counterclockwise to translate the lockingelement 306 in a distal direction, which removes the distal lip 310 fromthe recess 248 and unlocks the rod 114. The rod inserter 290 may then besafely removed from the surgical target site through the operativecorridor.

FIGS. 62-63 illustrate a third example of a rod inserter 312 configuredfor use with the spinal fixation system 110 according to anotherembodiment of the present invention. By way of example only, the rodinserter 312 is a mostly fixed-angle rod inserter that capable of slightvariation in the introduction angle that introduces the spinal rod 114through the operative corridor at one angle (relative to the inserter),and then allows for a slight adjustment in the angle (for example ±15°)for easier final seating of the rod 114 within the pedicle screw 112.

By way of example only, the rod inserter 312 includes a handle 314, ahousing tube 316, a rod holder 318, an attached driver 320, and a balllinkage 322. The housing tube 316 is an elongated cylindrical memberhaving an inner lumen extending throughout. The housing tube 316 may becurved so that the handle 314 is oriented at an angle (as opposed tolinear) relative to the operative corridor. This allows for improvedvisualization of the surgical target site by the surgeon as the rod isbeing inserted. The rod holder 318 is formed in the distal end of thehousing tube 316. The rod holder 318 includes a rod cavity 324 and alocking element 326. The rod cavity 324 is configured to receive thepost 246 of the spinal rod 114. The locking element 326 is positionedpartially within the rod holder 318 and partially within the inner lumenof the housing tube 316, and is moveable from a first unlocked positionto a second locked position. The locking element 326 includes a proximalrecess 328, a spring element 330, and a distal lip 332. The proximalrecess 328 is configured to receive the distal end of the ball linkage322. The spring element 330 helps to bias the locking element 326 in adistal direction. The distal lip 332 is configured to be seated withinthe recess 248 of the spinal rod 114 such that when the rod inserter 312is in the locked position, the spinal rod 114 is secured within the rodcavity 324 and will not become dislodged therefrom.

The rod inserter 312 includes an attached driver 320 at the proximal endof the handle 314. The driver 320 includes a drive shaft 334, a driverhandle 336, and a push button 338. The drive shaft 334 is partiallythreaded (and interacts with a partially threaded lumen inside thehandle 314) such that rotating the driver handle 336 in a clockwisedirection advances the drive shaft 334 in a distal direction, androtating the driver handle 336 in a counterclockwise direction retreatsthe drive shaft 334 in a proximal direction. The distal end of the driveshaft 334 abuts with the ball linkage 322, and thus distal advancementof the drive shaft 334 causes distal advancement of the ball linkage322. The ball linkage is a series of spheres abutting one another thatextend between the distal end of the drive shaft 334 and the proximalrecess 328 of the locking element 326. Further advancement of the driveshaft 334 will then cause the locking element 326 to engage the spinalrod 112 and lock it within the rod holder 318. Thus, the ball linkage322 enables direct control of the locking element 326 even though thehousing tube 316 is curved. The push button 338 provides an internalstop which allows the user to loosen the rod slightly (while stillretaining the rod) which allows for a slight adjustment in the angle(for example ±15°) for easier final seating of the rod 114 within thepedicle screw 112.

In use, the rod inserter 312 is initially provided without the spinalrod 114 and the rod holder 318 in an unlocked position. The spinal rod114 is then mated with the rod holder 318 by inserting the post 246 intothe rod cavity 324 such that the recess 248 is facing the lockingelement 326. The driver handle 336 is rotated in a clockwise direction,which as described above advances the locking element 326 in a distaldirection until the distal lip 332 of the locking element 326 is seatedwithin the recess 248. At this point the spinal rod 114 is secured tothe rod inserter 312. The rod 114 may be advanced through the operativecorridor using a guide assembly such as the guide assembly 116 (or anyof the other examples) described above. During final seating of the rod114 within the pedicle screw 112, it may become desirable to have aslight variation of the angle of insertion. This may be accomplished bypressing the push button 338, which loosens the rod 114 slightly (whilestill retaining the rod) which allows for a slight adjustment in theangle (for example ±15°). Once the rod 114 is seated within the pediclescrew 112 and secured as described above (and below), the rod 114 isready to be detached from the rod inserter 312. To accomplish this, thedriver handle 336 is turned counterclockwise to translate the lockingelement 326 in a distal direction, which removes the distal lip 332 fromthe recess 248 and unlocks the rod 114. The rod inserter 312 may then besafely removed from the surgical target site through the operativecorridor.

FIGS. 64-70 illustrate a reduction instrument 117 according to oneexample embodiment of the spinal fixation system 110. Generally, thereduction instrument 117 is used to fully seat (“reduce”) the spinal rod114 into the pedicle screw 112 and thereafter insert a lock screw 119 tosecure the rod 114 to the screw 112. The reduction instrument 117 isconfigured for use with any of the guide assemblies described above(e.g. 18, 116, 188, 224), however for the purpose of illustration thereduction instrument 117 will be described in use with the guideassembly 116 shown and described in relation to FIG. 21 et seq. Thereduction instrument 117 includes a connector 340 that releasablycouples the reduction instrument 117 to the guide assembly 116 (via thecap 128). The connector 340 has a guide cavity 342 into which theproximal end 122 of the outer sleeve 118 (featuring the cap 128) isreceived. The proximal end 122 is keyed to the guide cavity 342 so as toprevent rotation of the guide assembly 116 relative to the reductioninstrument 117. Spring locks 344 on the connector 340 are provided toprevent translation of the guide cap 128 and attached guide assembly 116relative to the reduction instrument 117. Specifically, the spring locks344 include ridges 346 that extend through the connector 340 into theguide cavity 342 and engage the circumferential groove 130 situatedbelow the proximal end 122 when the guide assembly 116 is mated with thereduction tool 117. The ridges 346 allow the proximal end 122 of theguide assembly 116 to push past the spring locks 344 until the ridges346 snap into place within the circumferential groove 130. To releasethe connection between the reduction instrument 117 and the guideassembly 116, the proximal ends of the spring locks 344 can be depressedcausing the ridges 346 to lift out of the circumferential groove 130,thus allowing the removal of the connector 128 from the guide cavity342.

The reduction instrument 117 has an elongated central shaft 348extending longitudinally through the entire length of reductioninstrument 117. The reduction instrument 117 further includes a rotationhandle 352, a translation handle 354, a threaded shaft 358, a spring362, an inner sleeve 364, and an outer sleeve 366. The central shaft 348has a proximal portion 349, a distal portion 350, and a block portion351 that is situated between the proximal portion 349 and the distalportion 350. The proximal portion 349 is generally cylindrical andextends proximally from the block portion 351 through the threaded shaft358, translation handle 354, and rotation handle 352. The distal portion350 is generally cylindrical (with a greater diameter than the proximalportion 349) and extends distally from the block portion 351. Therotation handle 352 extends through the translation handle 354 and has aproximal knob 353 configured for manipulation by a user. The rotationhandle is fixedly attached to the central shaft 348, and thus rotationof the rotation handle causes rotation of the central shaft 348. Therotation handle 352 may be provided with band markers 355 spaced apartat a specific distance (e.g. 10 mm) to indicate the amount of reduction.The translation handle 354 has a threaded aperture 356 that isdimensioned to receive the proximal end of the threaded shaft 358. Thetranslation handle 354 is rotatable in both clockwise andcounterclockwise directions. As will be explained, turning thetranslation handle 354 in a clockwise direction ultimately advances thecentral shaft 348 and reduces the spinal rod 114 into the pedicle screw112. As will be explained, the rotation handle 352 rotates independentlyof the translation handle 354 in both a clockwise and counterclockwisedirection, and turning the rotation handle 352 in a clockwise directionadvances the lock screw 119 into the housing 172 of the pedicle screw112.

The threaded shaft 358 is mated at its proximal end with the threadedaperture 356 of the translation handle 354 and engages with the centralshaft 348 at the proximal side of the block portion 351. An abutmentinsert 357 is positioned proximally of the block portion 351 andprovides an abutment surface for the threaded shaft 358. Rotation of thetranslation handle 354 causes the threaded shaft 358 to translate up ordown through the threaded aperture 356, translating the central shaft348 and rotation handle 352 up or down with it. The distal portion 350of the central shaft 348 extends distally from the block portion 351.The distal portion 350 extends through a spring 362 and an inner sleeve364. The spring 362 is positioned just distally of the block portion351, between the block portion 351 and the inner sleeve 364. The spring362 and inner sleeve 364 are contained within an outer sleeve 366. Thedistal portion 350 of the central shaft 348 has a distal roundedreduction end 361 that is configured to engage the spinal rod 114 andreduce it into the housing 172. Alternatively, the distal reduction end361 may be a generally planar rather than rounded (for example, FIGS.71-74 illustrate a reduction instrument 117 with a generally planarreduction end 361 a). A snap ring 368 is positioned within a recess 370formed just proximally of the distal rounded reduction end 361. The snapring 368 is sized and configured to prohibit passage of the lock screw119 until the spinal rod 114 is fully reduced into the housing 172 andan appropriate distal force is applied to the lock screw 119 by theinner shaft (as will be explained below). A lock screw engagementfeature 363 is provided on the distal portion 350 just proximally of therecess 370. The lock screw engagement feature 363 is configured totemporarily hold a lock screw 119 while preventing rotation of the lockscrew 119 relative to the central shaft 348. By way of example only, thelock screw engagement feature 363 may have a hexalobe shape as shown inFIGS. 64 and 74, however other shapes that prevent rotation of the lockscrew 119 relative to the central shaft 348 are possible. One or morewindows 372 may be formed in the outer sleeve 366 near the top of theinner sleeve 364. The windows 372 may provide a visual indication (forexample, a color coded indication) of when the rod 114 is fully reducedand the lock screw 119 is in position at the top of the housing 172awaiting engagement.

The lock screw 119 has a central aperture 374 configured to allowpassage of the distal portion 350 of the central shaft 348 therethrough.The central aperture 374 has a shape complimentary to the lock screwengagement feature 363 of the central shaft 348. By way of example only,that shape is hexalobe, however other shapes are possible. The lockscrew 119 also has a guide and advancement feature 376 such as by way ofexample, a helically wound flange feature disposed on the outercircumference of the lock screw 119. The guide and advancement feature376 mates with a complementary locking cap guide and advancement feature180 on the housing 172. The lock screw 119 engages the housing 172 viathe complementary guide and advancement features 180, 376 to press andlock the fixation rod 114 into the housing 172.

In use, once the pedicle screws 112 have been properly seated and a rod114 introduced, the reduction instrument 117 is engaged to a guideassembly 116 as previously described. At least one lock screw 119 isattached to the lock screw engagement feature 363 of the central shaft348. The translation handle 354 is operated in a clockwise direction toadvance the central shaft 348 in a distal direction such that the distalengagement end 361 contacts the spinal rod 114. At some point duringthis advancement, the lock screw 119 will come into contact with the topof the housing 172. However, because the central shaft 348 (and thus theset screw) is not rotating at this point, the set screw does not engagethe guide and advancement feature and advance into housing 172. However,the block portion 351 of the central shaft 348 continues to translatedistally, advancing the engagement end 361 through the central aperture374 of the lock screw 119 while the lock screw 119 remains stationaryatop the housing 172. The inner sleeve 364, which abuts the lock screw119 and extends proximally therefrom also remains stationary during thistime. Spring 362 allows this movement the of the engagement end 351relative to the lock screw 119. The spring 362, which is positionedbetween the block portion 351 and the inner sleeve 364, compresses dueto the transfer of translational energy from the block portion 351 tothe spring 362. This continues until the spinal rod 114 is fully reducedwithin the housing 172 of the pedicle screw 114, which may be indicatedwith a marker on the rotation handle (e.g. a green band near the top ofthe rotation handle that becomes hidden within the translation handlewhen the rod is fully reduced—not shown). For example, the rod 114 maybe fully reduced just before the rod bottoms out in the housing 172.This prevents excessive loads on the reducer from over reduction. Thoughnot shown, a stop may be provided to ensure reduction stops just priorto bottoming out. By way of example, the proximal end of the threadedshaft 358 may have a larger diameter than the threaded aperture 356 suchthat the proximal end can't pass out of the translation handle, therebystopping translation of the threaded shaft. At this point the lock screw119 is in position at top of the housing 172 of the pedicle screw 112,but the complementary guide and advancement features 180, 376 are notyet engaged. To do so, the rotation handle 352 may be briefly rotated ina clockwise or counterclockwise direction to align the guide andadvancement features on the lock screw 119 and housing 172. Though notnecessarily, an audible “click” may be heard, indicating that the guideand advancement features 180, 376 have initially mated and are ready forfull installation. The rotation handle 352 is then rotated in aclockwise direction. The engagement of the guide and advancementfeatures 180, 376 combined with the release of the energy contained inthe compressed spring push the lock screw 119 down the central shaft 348and into the housing 172. When the lock screw 119 is fully seated, therotation handle 354 will cease to rotate. To effect removal of thereduction instrument 117, the translation handle 354 is briefly turnedcounterclockwise (e.g. 10 mm) to back off reduction. The spring locks344 are disengaged as described above and the reduction instrument 117may be removed from the operative corridor.

FIGS. 75-77 illustrate a reduction instrument 380 according to anotherexample embodiment of the spinal fixation system 110. Generally, thereduction instrument 380 is used to fully seat (“reduce”) the spinal rod114 into the pedicle screw 112 and thereafter insert a lock screw 119 tosecure the rod 114 to the screw 112. The reduction instrument 380 isconfigured for use with any of the guide assemblies described above(e.g. 18, 116, 188, 224), however for the purpose of illustration thereduction instrument 380 will be described in use with the guideassembly 116 shown and described in relation to FIG. 21 et seq. Thereduction instrument 380 differs from the reduction instrument 117previously described in that the reduction instrument 380 uses a “pistolgrip” mechanism to cause translation of the central shaft 390 to reducethe rod 114. All other features are identical and it is to be understoodthat any feature previously described with respect to the reductioninstrument 117 may be provided on the reduction instrument 380 withoutdeparting from the scope of the present invention. The reductioninstrument 380 includes a connector 382 that releasably couples thereduction instrument 380 to the guide assembly 116 (via the cap 128).The connector 382 has a guide cavity 384 into which the proximal end 122of the outer sleeve 118 (featuring the cap 128) is received. Theproximal end 122 is keyed to the guide cavity 384 so as to preventrotation of the guide assembly 116 relative to the reduction instrument380. Spring locks 386 on the connector 382 are provided to preventtranslation of the guide cap 128 and attached guide assembly 116relative to the reduction instrument 380. Specifically, the spring locks386 include ridges 388 that extend through the connector 382 into theguide cavity 384 and engage the circumferential groove 130 situatedbelow the proximal end 122 when the guide assembly 116 is mated with thereduction tool 380. The ridges 388 allow the proximal end 122 of theguide assembly 116 to push past the spring locks 386 until the ridges388 snap into place within the circumferential groove 130. To releasethe connection between the reduction instrument 380 and the guideassembly 116, the proximal ends of the spring locks 386 can be depressedcausing the ridges 388 to lift out of the circumferential groove 130,thus allowing the removal of the connector 128 from the guide cavity384.

The reduction instrument 380 has an elongated central shaft 390extending longitudinally through the entire length of reductioninstrument 380. The reduction instrument 380 further includes a rotationhandle 392, a translation handle 394, a translation shaft 396, a spring(not pictured), an inner sleeve 398, and an outer sleeve 400. Thecentral shaft 390 has a proximal portion (not shown), a distal portion402, and a block portion 404 that is situated between the proximalportion and the distal portion 402. The proximal portion is generallycylindrical and extends proximally from the block portion 404 throughthe translation shaft 396 and rotation handle 392. The distal portion402 is generally cylindrical (with a greater diameter than the proximalportion) and extends distally from the block portion 404. The rotationhandle 392 extends through the translation handle 394 and has a proximalknob 393 configured for manipulation by a user. The rotation handle isfixedly attached to the central shaft 390, and thus rotation of therotation handle causes rotation of the central shaft 390. The rotationhandle 392 rotates independently of the translation handle 394 in both aclockwise and counterclockwise direction, and turning the rotationhandle 392 in a clockwise direction advances the lock screw 119 into thehousing 172 of the pedicle screw 112. The rotation handle 392 may beprovided with band markers 406 spaced apart at a specific distance (e.g.10 mm) to indicate the amount of reduction. The translation handle 394is provided in the form of a “pistol grip” handle, and includes astationary arm 408 joined with a pivot arm 410 at a first pivot point412. The stationary arm 408 is fixedly connected to the top of theconnector 382. The pivot arm 410 is connected to the stationary arm 408at a first pivot point 412, which comprises the distal ends of both thestationary arm 408 and the pivot arm 410. The pivot arm 410 is alsoconnected to the rotation handle 392 at a second pivot point 414, whichcauses advancement of the central shaft 390 when the pivot arm 410 ismoved. A lock bar 416 is pivotably attached to the pivot anti 410 and isprovided to maintain the translation handle 394 in a locked positionwhen the rod is fully reduced. The lock bar 416 extends through anaperture 418 formed in the stationary handle 408. By way of exampleonly, the lock par 416 may have a ratchet-type engagement with theaperture 418. Other locking engagements are possible.

The translation shaft 396 is mated at its proximal end with the rotationhandle 392 and engages with the central shaft 390 at the proximal sideof the block portion 404. The distal portion 402 of the central shaft390 extends distally from the block portion 404. The distal portion 402extends through a spring (not shown) and an inner sleeve 398. The springis positioned just distally of the block portion 404, between the blockportion 404 and the inner sleeve 398. The spring and inner sleeve 398are contained within an outer sleeve 400. The distal portion 402 of thecentral shaft 390 has a distal rounded reduction end 420 that isconfigured to engage the spinal rod 114 and reduce it into the housing172. Alternatively, the distal reduction end 420 may be a generallyplanar rather than rounded (for example, FIGS. 71-74 illustrate agenerally planar reduction end 361 a). A snap ring 422 is positionedwithin a recess formed just proximally of the distal rounded reductionend 420. The snap ring 422 is sized and configured to prohibit passageof the lock screw 119 until the spinal rod 114 is fully seated in thehousing 172 and an appropriate distal force is applied to the lock screw119 by the inner shaft (as will be explained below). The distal portion420 has a lock screw engagement feature as described above. One or morewindows 424 may be formed in the outer sleeve 400 near the top of theinner sleeve 398. The windows 424 may provide a visual indication (forexample, a color coded indication) of when the rod 114 is fully reducedand the lock screw 119 is in position at the top of the housing 172awaiting engagement. Alternatively, the final band marker 406 may bepositioned to disappear below the stationary handle 408 when the rod isfully reduced. The final band marker 406 may be colored (e.g. green) toaid visualization.

In use, once the pedicle screws 112 have been properly seated and a rod114 introduced, the reduction instrument 380 is engaged to a guideassembly 116 as previously described. At least one lock screw 119 isattached to the lock screw engagement feature of the central shaft 390.The translation handle 394 is operated by squeezing the pivot arm 410,which advances the central shaft 390 in a distal direction such that thedistal engagement end 420 contacts the spinal rod 114. At some pointduring this advancement, the lock screw 119 will come into contact withthe top of the housing 172. However, because the central shaft 390 isnot rotating at this point, the distal engagement end 420 continues toadvance through the central aperture 374 of the lock screw 119 while thelock screw 119 remains stationary atop the housing 172. The inner sleeve398, which abuts the lock screw 119 and extends proximally therefrom,consequently also remains stationary during this time as well. However,during this additional advancement (after the lock screw 119 has comeinto contact with the housing 172) the block portion 404 of the centralshaft 390 continues to advance distally. The spring, which is positionedbetween the block portion 404 and the inner shaft 398, compresses due tothe transfer of translational energy from the block portion 404 to thespring. This continues until the spinal rod 114 is fully reduced withinthe housing 172 of the pedicle screw 114. At this point the lock screw119 is in position at top of the housing 172 of the pedicle screw 112,but the complementary guide and advancement features are not yetengaged. To do so, the rotation handle 352 may be briefly rotated in aclockwise or counterclockwise direction to align the guide andadvancement features on the lock screw 119 and housing 172. Though notnecessarily, an audible “click” may be heard, indicating that the guideand advancement features 180, 376 have initially mated and are ready forfull installation. The rotation handle 352 is then rotated in aclockwise direction. The engagement of the guide and advancementfeatures combined with the release of the energy contained in thecompressed spring push the lock screw 119 down the central shaft 390 andinto the housing 172. When the lock screw 119 is fully seated, therotation handle 392 will cease to rotate. To effect removal of thereduction instrument 380, the translation handle 394 is briefly turnedcounterclockwise (e.g. 10 mm) to back off reduction. The spring locks344 are disengaged as described above and the reduction instrument 380may be removed from the operative corridor.

FIGS. 78-81 illustrate an example of an alternative reduction instrument430 according to another embodiment of the spinal fixation 110. Thereduction instrument 430 may preferably be used for reduction in asingle-level construct. The reduction instrument 430 is configured foruse with any of the guide assemblies described above (e.g. 18, 116, 188,224), however for the purpose of illustration the reduction instrument430 will be described in use with the guide assembly 116 shown anddescribed in relation to FIG. 21 et seq. By way of example only, thereduction instrument 430 includes a body 432, a handle 434, a fixedattachment assembly 436, and a translating attachment assembly 438. Thebody 432 includes a pair of elongated racks 440 arranged parallel to oneanother and joined at a proximal end by a generally curved connector442. The racks 440 each include a translation slot 444 configured toallow the translating attachment assembly 438 to translate freely inboth the proximal and distal directions. Each translation slot 444includes a plurality of rounded openings 446 configured to allow thetranslating attachment assembly 438 to rest easily in a single selectedposition without inhibiting the overall ability to translate. The handle434 is connected to the curved connector 442 via a shaft 448.

The fixed attachment assembly 436 is positioned between the distal endsof each of the racks 440 and is pivotably attached to each rack 440 viaa swivel pin 450. The translating attachment assembly 438 is positionedbetween the racks 440 and is capable of freely translating therealong.The translating attachment assembly 438 includes a swivel pin 452extending therethrough and having circular ends 454 that engage thetranslation slots 444 and rest in the rounded openings 446. The fixedattachment assembly 436 and translating attachment assembly 438 eachcomprise a connector 456 that attaches to the guide assembly 116 (viathe cap 128). The connector 456 has a guide cavity 458 into which theproximal end 122 of the outer sleeve 118 (featuring the cap 128) isreceived. The proximal end 122 is keyed to the guide cavity 458 so as toprevent rotation of the guide assembly 116 relative to the reductioninstrument 430. Spring locks 460 on the connector 456 are provided toprevent translation of the guide cap 128 and attached guide assembly 116relative to the reduction instrument 430. Specifically, the spring locks460 include ridges 462 that extend through the connector 456 into theguide cavity 458 and engage the circumferential groove 130 situatedbelow the proximal end 122 when the guide assembly 116 is mated with thereduction tool 430. The ridges 462 allow the proximal end 122 of theguide assembly 116 to push past the spring locks 460 until the ridges462 snap into place within the circumferential groove 130. The connector456 has a central aperture 464 formed there to allow passage of a lockscrew driver (not shown). To release the connection between thereduction instrument 430 and the guide assembly 116, the proximal endsof the spring locks 460 can be depressed causing the ridges 462 to liftout of the circumferential groove 130, thus allowing the removal of theconnector 128 from the guide cavity 458.

In use, once the pedicle screws 112 have been properly seated and a rod114 introduced, the reduction instrument 430 is employed by attachingthe fixed attachment assembly 436 to a first guide assembly 116 at afirst vertebral level and attaching the translating attachment assembly438 to a second guide assembly 116 on a adjacent vertebral level. Theattachment assemblies are attached to the guide assemblies in the mannerdescribed above. The handle 434 is then pushed downward (e.g. toward thespine), causing the body 432 to pivot around the translating attachmentassembly 438, thus lifting the fixed translation assembly 436. Thus thescrew 112, guide 116, and ultimately vertebra are lifted upward (i.e.reduced) to the desired position. A lock screw 119 is introduced via alock screw inserter (not shown) and attached to the housing 172 of thepedicle screw 112. The reduction instrument 430 can then be removed andthe lock screw 119 tightened via a final tightening device (not shown).

FIGS. 82-85 illustrate another alternative reduction instrument 470according to still another example embodiment of the spinal fixationsystem 110. Generally, the reduction instrument 470 is used to fullyseat (“reduce”) the spinal rod 114 into the pedicle screw 112 andthereafter insert a lock screw 119 to secure the rod 114 to the screw112. The reduction instrument 470 is configured for use with any of theguide assemblies described above (e.g. 18, 116, 188, 224), however forthe purpose of illustration the reduction instrument 470 will bedescribed in use with the guide assembly 116 shown and described inrelation to FIG. 21 et seq. The reduction instrument 470 includes aconnector body 472 that releasably couples the reduction instrument 470to the guide assembly 116 (via the cap 128). The connector body 472 hasa guide cavity 474 into which the proximal end 122 of the outer sleeve118 (featuring the cap 128) is received. The proximal end 122 is keyedto the guide cavity 474 so as to prevent rotation of the guide assembly116 relative to the reduction instrument 470. Spring locks 476 on theconnector body 472 are provided to prevent translation of the guide cap128 and attached guide assembly 116 relative to the reduction instrument470. Specifically, the spring locks 476 include ridges 477, as depictedin FIG. 82a , that extend through the connector 472 into the guidecavity 474 and engage the circumferential groove 130 situated below theproximal end 122 when the guide assembly 116 is mated with the reductiontool 470. The ridges allow the proximal end 122 of the guide assembly116 to push past the spring locks 476 until the ridges snap into placewithin the circumferential groove 130. To release the connection betweenthe reduction instrument 470 and the guide assembly 116, the proximalends 475 of the spring locks 476 can be depressed causing the ridges tolift out of the circumferential groove 130, thus allowing the removal ofthe connector 128 from the guide cavity 474.

The reduction instrument 470 includes a reduction assembly 478 and alock screw inserter 480. The reduction assembly includes a reductiontube 482, a threaded tubular shaft 484, and a reduction knob 486. Thereduction tube 482 has a proximal segment 488, a distal segment 490, anda lumen extending through the reduction tube 482 from the end of theproximal segment 488 to the end of the distal segment 490. The lumen atproximal segment 488 is threaded to threadedly engage the threadedtubular shaft 484. The distal segment 490 is configured to engage thespinal rod 114 in two points. The threaded tubular shaft 484 isconnected to the reduction knob 486 at its proximal end and theconnector body 472 at its distal end. The connection with the reductionknob 486 is fixed such that the rotation of the reduction knob 486causes the threaded tubular shaft 484 to rotate. The connection with theconnector body 472 is fixed axially but not fixed rotationally, suchthat the threaded tubular shaft 484 freely rotates against the connectorbody 472 without causing any rotation of the connector body 472. Theresult of this interaction is that upon rotation of the reduction knob486 (and threaded tubular shaft 484), the reduction tube 482 translatesin a distal direction relative to the connector body 472 (and attachedguide assembly 116). The end of the distal segment 490 will engage aspinal rod 114 placed within the guide assembly 116 (as described above)and reduce the spinal rod 114 into the pedicle screw 112.

The lock screw inserter 480 extends through the reduction assembly 478lock screw knob 492, a distal engagement post 494, and an elongatedshaft 496 extending between the lock screw knob 492 and distalengagement post 494. The distal engagement post 494 is configured toreceive a lock screw 119. By way of example only, the distal engagementpost 494 has a hexalobe configuration that is complementary to theaperture 374 of the lock screw 119 (FIG. 66). The distal engagement post494 further includes a snap ring 498 positioned within a recess 499. Thesnap ring 498 prevents premature ejection of the lock screw 119 duringthe implantation process.

In use, once the pedicle screws 112 have been properly seated and a rod114 introduced, the reduction instrument 470 is engaged to a guideassembly 116 as previously described. At least one lock screw 119 isattached to the distal engagement post 494 of the lock screw inserter480. The reduction knob 486 is operated in a clockwise direction (usingan appropriate attachment device) to advance the reduction tube 482 in adistal direction such that the distal engagement end 490 contacts thespinal rod 114. Operation of the reduction knob 486 is continued untilthe rod is fully reduced and seated within the housing 172 of thepedicle screw 112. At this point the lock screw 119 is in position attop of the housing 172 of the pedicle screw 112, but the complementaryguide and advancement features are not yet engaged. To do so, the lockscrew knob 492 may be briefly rotated in a clockwise or counterclockwisedirection until an audible “click” is heard, indicating that the guideand advancement features have initially mated and are ready for fullinstallation. The lock screw knob 492 is then rotated in a clockwisedirection and the lock screw 119 is introduced into the housing 172.When the lock screw 119 is fully seated, the lock screw knob 492 willcease to rotate. To effect removal of the reduction instrument 470, thereduction knob 486 is briefly turned counterclockwise (e.g. 10 mm) toback off reduction. The spring locks 476 are disengaged as describedabove and the reduction instrument 470 may be removed from the operativecorridor.

FIG. 86 illustrates an example of a compression instrument 500configured for use with the spinal fixation system 110 according to oneembodiment of the present invention. By way of example only, thecompression instrument 500 is a fulcrum pistol grip compressor with amain body 502, a rack 504, and a handle 506. The main body 502 includesa track 508 configured to receive the rack 504 and allow translationtherein. The rack 504 is an elongated body configured to be receivedwithin the track 508. The distal end of the rack 504 includes a tubularshaft 510 oriented generally orthogonally relative to the rack 504. Alock screw driver 512 extends through the tubular shaft 510 and isconfigured to be mated with a lock screw 119. The handle 506 ispivotably attached to the main body 502 via a pivot 514. A handle shaft516 extends from the distal end of the handle 506 and is configured tobe received within a guide assembly 116. The lock screw driver 512 andhandle shaft 516 are oriented in a generally parallel manner relative toone another. A push button 518 is provided on the distal end of the mainbody 502 and is configured to release the rack 504 when activated.

The compression instrument 500 may be used when at least one vertebrallevel to be fixed is in need of compression. Prior to using thecompression instrument 500, the pedicle screws 112 are put in place anda spinal rod 114 is seated therein. At one vertebral level, the spinalrod 114 is fully reduced and the lock screw 119 is secured to thepedicle screw. A first guide assembly 116 is attached to the pediclescrew at this first level. At the adjacent level to be compressed, thespinal rod 114 is fully reduced and the lock screw 119 is applied to thepedicle screw but not finally tightened. A second guide assembly 116 isattached to the pedicle screw 112 at this second level. To use thecompression instrument 500, the handle shaft 516 is inserted into thefirst guide assembly 116 and the lock screw driver 512 is inserted intothe second guide assembly 116 such that the distal end 519 of the lockscrew driver 512 engages the lock screw 119. During this insertion, thepush button 518 is depressed so that the rack 504 can move freely withinthe main body 502. This ensures proper alignment of the lock screwdriver 512 and the guide assembly 116, and engagement with the lockscrew 119. When proper alignment is achieved the push button 518 isreleased. The user then squeezes the handle 506, which compresses thevertebra by driving the first and second guide assemblies 116 (andattached screws and vertebrae) toward one another. Once the desiredcompression is achieved, the second lock screw 119 is tightened usingthe lock screw driver 512.

FIGS. 87-89 illustrate an alternative example of a compressioninstrument 520 according to another embodiment of the spinal fixationsystem 110. By way of example only, the compression instrument 520 is arack compressor for compressing the distance between adjacent vertebraprior to locking the spinal rod 114 in both pedicle screws 112. Thecompression instrument 520 includes a rack 522 with a fixed arm 524 anda moveable arm 526. The rack 522 includes a plurality of teeth 523provided along one side of the rack 522 and extending substantially thelength of the rack 522. The fixed arm 524 is positioned at a first endof the rack 522 and includes a fixed base 528 that is attached to therack 522 and a removable arm member 530 that includes an attachmentelbow 532, an elongated arm 534, and a hoop 536. The fixed base 528includes a cylindrical post 538 extending laterally from the fixed base528 and a fixed gear wheel 540 at the base of the post 538 and adjacentthe fixed base 528. The attachment elbow 532 extends laterally from theproximal end of the elongated arm 534 and has an aperture 542 andassociated lumen for receiving the post 538. The aperture 542 containsgear slots that mate with the gear wheel 540. The hoop 536 is positionedat the distal end of the elongated arm 534 and is configured foradvancement over a guide assembly 116. The moveable arm 526 includes atranslating base 544 that is capable of translating along the rack 522and a removable arm member 546 that includes an attachment elbow 548, anelongated arm 550, and a hoop 552. The translating base 544 includes acylindrical post 554 extending laterally from the translating base 544and a fixed gear wheel 556 at the base of the post 554 and adjacent thebase 544. The attachment elbow 548 extends laterally from the proximalend of the elongated arm 550 and has an aperture 558 and associatedlumen for receiving the post 554. The aperture 558 contains gear slotsthat mate with the gear wheel 556. The hoop 552 is positioned at thedistal end of the elongated arm 550 and is configured for advancementover a guide assembly 116. This configuration allows the compressor armsto be attached to the rack assembly at a variety of angles.

The translating base 544 includes a user selectable lock 560 thatprevents translation in an undesired direction (e.g. moving arms awayfrom each other when compression is desired and moving arms toward eachother when distraction is desired). The lock 560 includes a selectorswitch 562, a first pawl 564, a second pawl 566. The selector switch 562is pivotably attached to the translating base 544 and includes generallysmooth rounded pawl interface 568 and a recess 570 formed therein. Thefirst pawl 564 is pivotably connected to the translating base 544 andincludes a first end 572 and a second end 574. The first end 572 isgenerally rounded and dimensioned to be received within the recess 570on the selector switch 562. The second end 574 includes a ratchet and isconfigured to engage the ridges 523 of the rack 522 to prevent movementof the translating arm 526 away from the fixed arm 524. The second pawl566 is pivotably connected to the translating base 544 and includes afirst end 576 and a second end 578. The first end 576 is generallyrounded and dimensioned to be received within the recess 570 on theselector switch 562. The second end 578 includes a ratchet and isconfigured to engage the ridges 523 of the rack 522 to prevent movementof the moveable arm 526 toward the fixed arm 524. The translating base544 further includes a turnkey 580 that a user may manipulate to causethe translating arm 526 to translate along the rack 522. The turnkey 580is attached to the translating base 544 and interacts with the teeth 523of the rack 522 via a rotating gear 582.

In use, when the turnkey 580 is operated to move the movable arm 526towards the fixed arm 524 the guide assembly 116 (and thus pedicle screw112 and attached vertebra) that the moveable arm 526 is attached tomoves towards the other one, compressing the distance between theadjacent vertebrae. The principle also works in reverse to distract thevertebrae. The selector switch 562 is configured to adjust the lock 560between a compression position (which allows compression and preventsdistraction), a distraction position (which allows distraction andprevents compression), and an open position (which allows the moveablearm 526 to move in either direction along the rack 522). The selectorswitch 562 is configured to point in the general direction of thedesired movement. When the lock 560 is in the compression position, therecess 570 is engaged with the first end 572 of the first pawl 564. Thiswill force the second end 574 to engage the teeth 523 of the rack 522and prevent movement of the moveable arm 526 away from the fixed arm524. Simultaneously, the rounded surface 568 of the selector switch 562forces the first end 576 end of the second pawl 566 (relatively) down,such that the second end 578 is unable to engage the teeth 523 of therack 522. This allows for translation of the moveable arm 526 in thecompression direction while preventing such movement in the distractiondirection. Likewise, when the lock 560 is in the distraction position,the recess 570 is engaged with the first end 576 of the second pawl 566.This will force the second end 578 to engage the teeth 523 of the rack522 and prevent movement of the moveable arm 526 toward the fixed arm524. Simultaneously, the rounded surface 568 of the selector switch 562forces the first end 572 end of the first pawl 564 (relatively) down,such that the second end 574 is unable to engage the teeth 523 of therack 522. This allows for translation of the moveable arm 526 in thedistraction direction while preventing such movement in the compressiondirection. When the selector switch 562 is in the open position, therecess 570 does not engage either of the first and second pawls 564,566. The rounded surface 568 engages the first end 572 of the first pawl564 and also the first end 576 of the second pawl 566, forcing them both(relatively) down. The result is that neither pawl 564, 566 is engagedwith the teeth 523 of the rack 522, and the moveable arm 526 is able totranslate in either direction and effect both distraction andcompression.

FIGS. 90-96 illustrate an example of a multi-load lock screw inserter590 configured for use with the spinal fixation system 110 according toone embodiment of the present invention. The multi-load lock screwinserter 590 is useful in that multiple lock screws 119 may be loaded onto the driver 590 such that a user may quickly move among multiple guideassemblies 116 and anchors 112 without having to load a new lock screw119 each time. By way of example only, the multi-load lock screwinserter 590 includes a handle 592 and a central shaft 594 extendingdistally from the handle 592. The multi-load lock screw inserter 590further includes a spring 596, an inner sleeve 598, and an outer sleeve600. The spring 596 is positioned between the handle 592 and the innersleeve 598. The spring is contained within the outer sleeve 600. Thecentral shaft 594 extends through the spring 596, inner sleeve 598, andouter sleeve 600. The proximal end of the inner sleeve 598 abuts thedistal end of the spring 596. The distal end of the inner sleeve 598 isalways in contact with the proximal-most lock screw 119.

The distal portion of the central shaft 594 includes a drive feature 602that is configured to retain and control the rotation of the attachedlock screws 119. By way of example only, the drive feature 602 may havea hexalobe shape, however other shapes that prevent rotation of the lockscrew 119 relative to the central shaft 594 are possible. A snap ring604 is positioned within a recess formed just proximally of the distalend of the central shaft 594. The snap ring 604 is sized and configuredto prohibit passage of the lock screw(s) 119 until an appropriate distalforce is applied to the lock screw 119 by the inner sleeve 598 and/or arotational engagement with a pedicle screw.

In use, as multiple lock screws 119 are loaded onto the multi-load lockscrew inserter 590, the proximal-most lock screw 119 forces the innersleeve 598 in proximal direction, which causes the spring 596 tocompress. As lock screws 119 are engaged to pedicle screws (and removedfrom the multi-load lock screw inserter 590), the spring 596 exerts adistal force on the inner sleeve 598, which in turn pushes the next lockscrew 119 into position. In this fashion, a user may quickly move amongmultiple guide assemblies 116 and anchors 112 without having to load anew lock screw 119 each time.

FIGS. 97-98 illustrate an example of a guide adjuster 610 for use withthe spinal fixation system 110 of the present invention. The guideadjuster 610 is configured for use with any of the guide assembliesdescribed above, however for the purpose of illustration the guideadjuster 610 will be described in use with the guide assembly 116 shownand described in relation to FIG. 21 et seq. The guide adjuster 610 isuseful when the guide assemblies 116 are in need of twisting in order toalign the guide channels. By way of example only, the guide adjuster 610includes a handle 612 and a guide cavity 614. The handle 612 includes apair of arms 616 enabling a user to manipulate the guide adjuster 610.The guide cavity 614 is configured to receive the proximal end 122 ofthe outer sleeve 118 (featuring the cap 128). The proximal end 122 iskeyed to the guide cavity 614 so as to prevent rotation of the guideassembly 116 relative to the guide adjuster 610.

FIGS. 99-100 illustrate an example of a tap guide 620 including a catchmechanism for use with the spinal fixation system of the presentinvention. Generally, the catch mechanism is spring loaded to catch thetap in a contained position (distal end contained within dilator).Pressing the catch release allows the tap to be advanced past the distalend of the dilator. Once the hole is tapped, the tap can be pulled backand again locked in the contained position for removal. By way ofexample only, the tap guide 620 is a generally tubular elongated memberhaving a shaft 622 with a lumen 624 extending therethrough. The outersurface 626 of the shaft 622 includes rifling 628, which facilitatesinsertion into the operative corridor. The proximal end of the shaft 622is equipped with a catch mechanism which includes a retention tab 630, aspring 632, a retaining pin 634, and a catch release button 636. Theretention tab 630 retains the tap (not shown) in the tap guide 620during insertion into and removal from the surgical target site. Thisretention is facilitated by the spring 632. Once docked on the pedicle,the catch release button 636 may be pressed, allowing the tap to passsuch that the distal end of the tap can extend past the end of the tapguide 620 for tapping of the pedicle. The distal end 638 of the shaft622 includes a choke feature which facilitates the alignment of thetool.

FIG. 101 illustrates an example of an offset dilator 640 configured foruse with the spinal fixation system 110 according to one embodiment ofthe present invention. By way of example only, the offset dilator 640includes a tubular shaft 642 having a lumen 644 extending therethrough.A longitudinal groove 646 is formed along the outer surface of theoffset dilator 640 and is configured to receive a K-wire (not shown).The offset dilator 640 may have a shaped proximal end 648 for ease ofmanipulation. The offset dilator 640 may be used to expose the facet fordecortications and fusion. The offset dilator 640 is advanced over theK-wire via the longitudinal groove 646. The offset dilator 640 can thenbe rotated around the K-wire until the lumen 644 is centered over thefacet.

FIGS. 102-103 illustrate an alternative example of an offset dilator 650configured for use with the spinal fixation system 110 according toanother embodiment of the present invention. By way of example only, theoffset dilator 650 includes a tubular shaft 652 having a lumen 654extending therethrough. A longitudinal groove 656 is formed along theouter surface of the offset dilator 650 and is configured to receive aK-wire (not shown). The offset dilator 650 may have a shaped proximalend 658 for ease of manipulation. The offset dilator 650 furtherincludes a lateral slot 659 that is dimensioned to receive a light cable(not shown). The offset dilator 650 may be used to expose the facet fordecortications and fusion. The offset dilator 650 is advanced over theK-wire via the longitudinal groove 656. The offset dilator 650 can thenbe rotated around the K-wire until the lumen 654 is centered over thefacet. Once the offset dilator 650 is in position, a light cable may beemployed in the lateral slot 659 to introduce light to the surgicaltarget site.

FIG. 104 is an example of a secondary dilator 660 positioned within theoffset dilators 640, 650 to facilitate advancement to the surgicaltarget site. The secondary dilator 660 has an elongated tubular shaft662 and a lumen 664 extending therethrough.

FIGS. 105-108 illustrate an example of an alternative rod inserter 670for use with the spinal fixation system 110 according to anotherembodiment of the present invention. The rod inserter 670 is capable oflockingly engaging the cylindrical body portion of a spinal rod (asopposed to one of the ends). By way of example only, the rod inserter670 includes a handle 672, a shaft sleeve 674, and a shaft 676. Thehandle 672 has an interior lumen 678. The shaft 676 is an elongatedcylindrical member having a proximal threaded region 680 and a distalrod retaining head 682. The proximal threaded region 680 is threadedlyreceived within a rotating knob 684 positioned on the proximal end ofthe handle 672. The distal rod retaining head 682 is formed from a pairof prongs 686 that cooperate to form a semi-cylindrical recess 688 thatis configured to receive a spinal rod (not shown). A small slot 690 isformed in the shaft 676 at the distal end to allow for expansion and/orcontraction of the rod retaining head 682 during rod engagement. Theouter sleeve 674 includes a distal cavity 692 for receiving the rodretaining head 682 when a spinal rod is engaged and the rod inserter 670is in a locked position. The shaft 694 includes a translation slot 694configured to receive a translation pin 696 that is secured to the outersleeve 674. The translation slot 694 and pin 696 combination serve tocontrol and limit the amount of translation the shaft 676 is capable of.By way of example only, the slot 694 allows for approximately 5 mm oftranslation. The rotating knob 684 is secured to the handle 672 by wayof an internal ring 698.

In use, a spinal rod is placed into the recess 688 at the distal end ofthe shaft 676. The rotating knob 684 is turned clockwise, which causesthe shaft 676 to translate in a proximal direction. The distal rodretaining head 682 is then drawn into the distal cavity 692 of the outersleeve 674. This effectively locks the spinal rod to the rod holder 670as the prongs 686 are squeezed together by the distal cavity 692.

While the inventive features described herein have been described interms of a preferred embodiment for achieving the objectives, it will beappreciated by those skilled in the art that variations may beaccomplished in view of these teachings without deviatin from the spiritor scope of the invention. Also, while this invention has been describedaccording to a preferred use in spinal applications, it will beappreciated that it may be applied to various other uses desiringsurgical fixation, for example, the fixation of long bones.

What is claimed is:
 1. A guide assembly for use with a spinal fixationsystem, the guide assembly comprising: an outer sleeve comprising anouter sleeve proximal end and an outer sleeve distal portion, the outersleeve distal portion including a ridge configured to mate with a slotin an anchor element to secure the outer sleeve to the anchor element;an inner arm assembly positioned within the outer sleeve, the inner armassembly comprising first and second inner arm members positioned withinthe outer sleeve, wherein the first inner arm member comprises a firstinner arm distal portion and the second inner arm member comprises asecond inner arm distal portion, the first and second inner arm distalportions configured to engage the anchor element; and an actuatormoveable to cause translation of the first and second inner arm membersfrom a first position to a second position with respect to the outersleeve, whereby in the second position the first and second inner armdistal portions are in a locked engagement with the anchor element,wherein the actuator is a visual indicator configured to alert a userthat the first and second inner arm distal portions are in a lockedengagement, wherein the actuator comprises an actuator proximal end andan actuator distal end, wherein when the first and second inner armmembers are in the second position the actuator proximal end is flushwith the outer sleeve proximal end and the actuator distal end is distalof the outer sleeve proximal end, and when the first and second innerarm members are in the first position the actuator protrudes proximallyfrom the outer sleeve proximal end.
 2. The guide assembly of claim 1,wherein the actuator comprises a castle nut, wherein the inner armassembly comprises an inner arm assembly proximal portion which isattached directly to the castle nut.
 3. The guide assembly of claim 2,wherein the inner arm assembly proximal portion includes a grooveengaging a corresponding ridge in an interior of the castle nut.
 4. Aguide assembly for use with a spinal fixation system, the guide assemblycomprising an outer sleeve and independent first and second inner armmembers positioned within the outer sleeve, the outer sleeve having adistal portion including a ridge configured to mate with a slot in ananchor element to secure the outer sleeve to the anchor element, thefirst and second inner arm members configured to engage the anchorelement, the guide assembly further comprising an actuator moveable tocause translation of the first and second inner arm members from a firstposition to a second position, whereby in the second position the firstand second inner arm members are in a locked engagement with the anchorelement, wherein the actuator serves as a visual indicator configured toalert a user that the first and second inner arm members are in a lockedengagement, wherein the actuator does not protrude from a proximal endof the outer sleeve when the first and second inner arm members are inthe second position, and the actuator protrudes from the proximal end ofthe outer sleeve when the first and second inner arm members are in thefirst position.
 5. The guide assembly of claim 4, wherein the actuatoris a castle nut.
 6. The guide assembly of claim 5, wherein the first andsecond inner arm members extend distally from an inner arm memberproximal portion, and the inner arm member proximal portion includes agroove that is dimensioned to engage a corresponding ridge in theinterior of the castle nut.
 7. The guide assembly of claim 4, whereinthe first and second inner arm members are spaced apart at apredetermined distance, the predetermined distance defining a channelfor guiding the spinal rod into the rod channel of the anchor assembly.8. The spinal fixation system of claim 4, wherein the first and secondinner arm members each have a distal engagement feature, the distalengagement feature comprising first and second prongs, wherein uponengagement with the anchor element, the first prong aligns on one sideof an upstanding arm of the anchor element and the second prong alignson the other side of said upstanding arm of the anchor element, whereinthe first and second prongs each have a cutout formed therein, thecutout configured to mate with a vertical recess in the anchor element.9. The guide assembly of claim 4 is configured for use with a spinalfixation system, comprising: a plurality of anchor assemblies, eachanchor assembly having a housing member, a threaded shaft, and a lockscrew, the housing member having a rod channel between a pair ofupstanding arms, the upstanding arms each having a slot formed in anoutside surface thereof; and an elongated spinal rod dimensioned to spanthe distance between at least two adjacent vertebral structures.
 10. Thespinal fixation system of claim 9, wherein the actuator is a castle nut.11. The guide assembly of claim 10, wherein the first and second innerarm members extend distally from an inner arm member proximal portion,and the inner arm member proximal portion includes a groove that isdimensioned to engage a corresponding ridge in the interior of thecastle nut.
 12. The spinal fixation system of claim 9, wherein the firstand second inner arm members each have a distal engagement feature, thedistal engagement feature comprising first and second prongs, whereinupon engagement with the anchor element, the first prong aligns on oneside of an upstanding arm of the anchor element and the second prongaligns on the other side of said upstanding arm.
 13. The spinal fixationsystem of claim 12, wherein the distal engagement feature furthercomprises a protrusion positioned between the first and second prongs,the protrusion configured to mate with a slot formed in a top surface ofsaid upstanding arm.
 14. The spinal fixation system of claim 9, whereinthe first and second inner arm members are spaced apart at apredetermined distance, the predetermined distance defining a channelfor guiding the spinal rod into the rod channel of the anchor assembly.15. The spinal fixation system of claim 9, wherein the anchor assemblieseach have a vertical recess cut into upstanding arms on either side ofthe rod channel, the vertical recesses formed orthogonally relative tothe rod channel.
 16. The spinal fixation system of claim 15, wherein thefirst and second inner arm members each have a distal engagementfeature, the distal engagement feature comprising first and secondprongs, wherein upon engagement with the anchor element, the first prongaligns on one side of an upstanding arm of the anchor element and thesecond prong aligns on the other side of said upstanding arm, whereinthe first and second prongs each have a cutout formed therein, thecutout configured to mate with the vertical recesses.
 17. The spinalfixation system of claim 9, further comprising: a second guide assemblycomprising an outer sleeve and a pair of independent arm memberspositioned within the outer sleeve, the outer sleeve having a distalportion including a ridge configured to mate with the slot in a secondanchor element to secure the outer sleeve to the second anchor element,the arm members configured to engage the anchor element, the secondguide assembly further comprising an actuator moveable to causetranslation of the first and second inner arm members from a firstposition to a second position, whereby in the second position the firstand second inner arm members are in a locked engagement with the secondanchor element.